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PHP Interview Question & Answer

PHP

1. What are the differences between GET and POST methods in form submitting, give the case where we can use get and we can use post methods?
Answer:
On the server side, the main difference between GET and POST is where the submitted is stored. The $_GET array stores data submitted by the GET method. The $_POST array stores data submitted by the POST method.
On the browser side, the difference is that data submitted by the GET method will be displayed in the browser's address field. Data submitted by the POST method will not be displayed anywhere on the browser.
GET method is mostly used for submitting a small amount and less sensitive data. POST method is mostly used for submitting a large amount or sensitive data.

2. Who is the father of php and explain the changes in php versions?
Answer:
Rasmus Lerdorf for version changes go to http://php.net/
Marco Tabini is the founder and publisher of php|architect.

3. How can we submit from without a submit button?
Answer:
We can use a simple JavaScript code linked to an event trigger of any form field.
In the JavaScript code, we can call the document.form.submit() function to submit
the form. For example:

4. How many ways we can retrieve the date in result set of mysql Using php?
Answer:
As individual objects so single record or as a set or arrays.

5. What is the difference between mysql_fetch_object and mysql_fetch_array?
Answer:
MySQL fetch object will collect first single matching record where mysql_fetch_array will collect all matching records from the table in an array.



6. What is the difference between $message and $$message?
Answer:
They are both variables. But $message is a variable with a fixed name. $$message is a variable who's name is stored in $message. For example, if $message contains "var", $$message is the same as $var.

7. How can we extract string 'abc.com ' from a string
'http://info@a...' using regular _expression of php?

Answer:
We can use the preg_match() function with "/.*@(.*)$/" as
the regular expression pattern. For example:
preg_match("/.*@(.*)$/","http:// info@abc.com ",$data);
echo $data[1];

8. How can we create a database using php and mysql?
Answer:
PHP: mysql_create_db()
Mysql: create database;

9. What are the differences between require and include, include_once?
Answer:
File will not be included more than once. If we want to include a file once only and further calling of the file will be ignored then we have to use the PHP function include_once(). This will prevent problems with function redefinitions, variable value reassignments, etc.

10. Can we use include ("abc.php") two times in a php page "makeit.php"?
Answer:
Yes we can include..

11. What are the different tables present in mysql, which type of table is generated when we are creating a table in the following
syntax: create table employee(eno int(2),ename varchar(10)) ?

Answer:
Total 5 types of tables we can create
1. MyISAM
2. Heap
3. Merge
4. InnoDB
5. ISAM
6. BDB
MyISAM is the default storage engine as of MySQL 3.23.

12. Functions in IMAP, POP3 AND LDAP?
Answer:
Please visit:
http://fi2.php.net/imap
http://uk2.php.net/ldap

13. How can I execute a php script using command line?
Answer:
Just run the PHP CLI (Command Line Interface) program and provide the PHP script file name as the command line argument. For example, "php myScript.php", assuming "php" is the command to invoke the CLI program.
Be aware that if your PHP script was written for the Web CGI interface, it may not execute properly in command line environment.

14. Suppose your ZEND engine supports the mode <? ?> Then how can u configure your php ZEND engine to support <?php ?> mode ?
Answer:
If you change the line: short_open_tag = off in php.ini file. Then your php ZEND engine support only <?php ?> mode.

15. Shopping cart online validation i.e. how can we configure the paypals?
16. What is meant by nl2br()?
Answer:
nl2br -- Inserts HTML line breaks before all newlines in a string
string nl2br (string); Returns string with '<br />' inserted before all newlines.
For example: echo nl2br("god blessn you") will output "god bless
n you" to your browser.

17. Draw the architecture of ZEND engine?
18. What are the current versions of apache, php, and mysql?
Answer:
PHP: php5.1.2
MySQL: MySQL 5.1
Apache: Apache 2.1

19. What are the reasons for selecting lamp (Linux, apache, mysql, php) instead of combination of other software programs, servers and operating systems?
Answer:
All of those are open source resource. Security of linux is very very more than windows. Apache is a better server that IIS both in functionality and security. Mysql is world most popular open source database. Php is more faster that asp or any other scripting language.

20. How can we encrypt and decrypt a data present in a mysql table using mysql?
Answer:
AES_ENCRYPT () and AES_DECRYPT ()




21. How can we encrypt the username and password using php?
Answer:
You can encrypt a password with the following Mysql>SET PASSWORD=PASSWORD("Password");
We can encode data using base64_encode($string) and can decode using base64_decode($string);

22. What are the features and advantages of OBJECT ORIENTED PROGRAMMING?
Answer:
One of the main advantages of OO programming is its ease of modification; objects can easily be modified and added to a system there by reducing maintenance costs. OO programming is also considered to be better at modeling the real world than is procedural programming. It allows for more complicated and flexible interactions. OO systems are also easier for non-technical personnel to understand and easier for them to participate in the maintenance and enhancement of a system because it appeals to natural human cognition patterns.
For some systems, an OO approach can speed development time since many objects are standard across systems and can be reused. Components that manage dates, shipping, shopping carts, etc. can be purchased and easily modified for a specific system.

23. What are the differences between PROCEDURE ORIENTED LANGUAGES AND OBJECT ORIENTED LANGUAGES?
Answer:
Traditional programming has the following characteristics:
Functions are written sequentially, so that a change in programming can affect any code that follows it.
If a function is used multiple times in a system (i.e., a piece of code that manages the date), it is often simply cut and pasted into each program (i.e., a change log, order function, fulfillment system, etc). If a date change is needed (i.e., Y2K when the code needed to be changed to handle four numerical digits instead of two), all these pieces of code must be found, modified, and tested.
Code (sequences of computer instructions) and data (information on which the instructions operates on) are kept separate. Multiple sets of code can access and modify one set of data. One set of code may rely on data in multiple places. Multiple sets of code and data are required to work together. Changes made to any of the code sets and data sets can cause problems through out the system.
Object-Oriented programming takes a radically different approach:
Code and data are merged into one indivisible item – an object (the term “component” has also been used to describe an object.) An object is an abstraction of a set of real-world things (for example, an object may be created around “date”) The object would contain all information and functionality for that thing (A date
object it may contain labels like January, February, Tuesday, Wednesday. It may contain functionality that manages leap years, determines if it is a business day or a holiday, etc., See Fig. 1). Ideally, information about a particular thing should reside in only one place in a system. The information within an object is encapsulated (or hidden) from the rest of the system.
A system is composed of multiple objects (i.e., date function, reports, order processing, etc., See Fig 2). When one object needs information from another object, a request is sent asking for specific information. (for example, a report object may need to know what today’s date is and will send a request to the date object) These requests are called messages and each object has an interface that manages messages.
OO programming languages include features such as “class”, “instance”, “inheritance”, and “polymorphism” that increase the power and flexibility of an object.

24. What is the use of friend function?
Answer:
Friend functions
Sometimes a function is best shared among a number of different classes. Such functions can be declared either as member functions of one class or as global functions. In either case they can be set to be friends of other classes, by using a friend specifier in the class that is admitting them. Such functions can use all attributes of the class whichnames them as a friend, as if they were themselves members of that class.
A friend declaration is essentially a prototype for a member function, but instead of requiring an implementation with the name of that class attached by the double colon syntax, a global function or member function of another class provides the match.
class mylinkage {
private:
mylinkage * prev;
mylinkage * next;
protected:
friend void set_prev(mylinkage* L, mylinkage* N);
void set_next(mylinkage* L);
public:
mylinkage * succ();
mylinkage * pred();
mylinkage();
};
void mylinkage::set_next(mylinkage* L) { next = L; }
void set_prev(mylinkage * L, mylinkage * N ) { N->prev = L; }
Friends in other classes
It is possible to specify a member function of another class as a friend as follows:
class C {
friend int B::f1();
};
class B {
int f1();
};
It is also possible to specify all the functions in another class as friends, by specifying the entire class as a friend.
class A {
friend class B;
};
Friend functions allow binary operators to be defined which combine private data in a pair of objects. This is particularly powerful when using the operator overloading features of C++. We will return to it when we look at overloading.

25. What are the differences between public, private, protected, static, transient, final and volatile?
element Class Interface
Data field Method Constructor
modifier top level nested top level nested
(outer) (inner) (outer) (inner)
final yes yes no yes yes no no
private yes yes yes no yes no yes
protected yes yes yes no yes no yes
public yes yes yes yes yes yes yes
static yes yes no no yes no yes
transient yes no no no no no no
volatile yes no no no no no no

26. What are the different types of errors in php?
Answer:
Three are three types of errors:
1. Notices: These are trivial, non-critical errors that PHP encounters while executing a script - for example, accessing a variable that has not yet been defined. By default, such errors are not displayed to the user at all - although, as you will see, you can change this default behaviour.
2. Warnings: These are more serious errors - for example, attempting to include() a file which does not exist. By default, these errors are displayed to the user, but they do not result in script termination.
3. Fatal errors: These are critical errors - for example, instantiating an object of a non-existent class, or calling a non-existent function. These errors cause the immediate termination of the script, and PHP's default behaviour is to display them to the user when they take place.

27. What is the functionality of the function strstr and stristr?
Answer:
strstr() returns part of a given string from the first occurrence of a given substring to the end of the string. For example: strstr(" user@example.com ","@") will return "@example.com".
stristr() is idential to strstr() except that it is case insensitive.
28. What are the differences between PHP 3 and PHP 4 and PHP 5?
Answer:
Go read the release notes at http://php.net.

29. How can we convert asp pages to php pages?
Answer:
You can download asp2php front-end application from the site http://asp2php.naken.cc.

30. What is the functionality of the function htmlentities? Answer: htmlentities -- Convert all applicable characters to HTML entities
This function is identical to htmlspecialchars() in all ways, except with htmlentities(), all characters which have HTML character entity equivalents are translated into these entities.

31. How can we get second of the current time using date function?
Answer:
$second = date(“s”);

32. How can we convert the time zones using php?
Answer:
<?
echo "Original Time: ". date("h:i:s")."n";
putenv("TZ=US/Eastern");
echo "New Time: ". date("h:i:s")."n";
?>

33. What is meant by urlencode and urldocode?
Answer:
urlencode() returns the URL encoded version of the given string. URL coding converts special characters into % signs followed by two hex digits. For example: urlencode("10.00%") will return "10%2E00%25". URL encoded strings are safe to be used as part of URLs.
urldecode() returns the URL decoded version of the given string.

34. What is the difference between the functions unlink and unset?
Answer:
unlink() deletes the given file from the file system.
unset() makes a variable undefined.

35. How can we register the variables into a session?
Answer:
We can use the session_register ($ur_session_var) function.

36. How can we get the properties (size, type, width, height) of an image using php image functions?
Answer:
To know the Image type use exif_imagetype () function
To know the Image size use getimagesize () function
To know the image width use imagesx () function
To know the image height use imagesy() function

37. How can we get the browser properties using php?
Answer:
<?php
echo $_SERVER['HTTP_USER_AGENT'] . "nn";
$browser = get_browser(null, true);
print_r($browser);
?>

38. What is the maximum size of a file that can be uploaded using php and how can we change this?
Answer:
You can change maximum size of a file set upload_max_filesize variable in php.ini file

39. How can we increase the execution time of a php script?
Answer:
Set max_execution_time variable in php.ini file to your desired time in second.

40. How can we take a backup of a mysql table and how can we restore it.?
Answer: Create a full backup of your database: shell> mysqldump --tab=/path/to/some/dir --opt db_name Or: shell> mysqlhotcopy db_name /path/to/some/dir
The full backup file is just a set of SQL statements, so restoring it is very easy:
shell> mysql < backup_sunday_1_PM.sql




41. How can we optimize or increase the speed of a mysql select query?
Answer:
In general, when you want to make a slow SELECT … WHERE query faster, the first thing to check is whether you can add an index. All references between different tables should usually be done with indexes. You can use the EXPLAIN statement to determine which indexes are used for a SELECT.
Some general tips for speeding up queries on MyISAM tables:
A: To help MySQL better optimize queries, use ANALYZE TABLE or run myisamchk --analyze on a table after it has been loaded with data. This updates a value for each index part that indicates the average number of rows that have the same value. (For unique indexes, this is always 1.) MySQL uses this to decide which index to choose when you join two tables based on a non-constant expression. You can check the result from the table analysis by using SHOW INDEX FROM tbl_name and examining the Cardinality value. myisamchk --description --verbose shows index distribution information.

42. How many ways can we get the value of current session id?
Answer:
session_id() returns the session id for the current session.

43. How can we destroy the session, how can we unset the variable of a session?
Answer:
session_unregister() unregisters a global variable from the current session.
session_unset() frees all session variables.

44. How can we destroy the cookie?
Answer::
Set the cookie in past.

45. How many ways we can pass the variable through the navigation between the pages?
Answer:
At least 3 ways:
a) Register the variable into the session
b) Pass the variable as a cookie
c) Pass the variable as part of the URL
46. What is the difference between ereg_replace() and eregi_replace()?
Answer:
eregi_replace() function is identical to ereg_replace() except that this ignores case distinction when matching alphabetic characters.

47. What are the different functions in sorting an array?
Answer:
Sorting functions in PHP:
asort()
arsort()
ksort()
krsort()
uksort()
sort()
natsort()
rsort()

48. How can we know the count/number of elements of an array?
Answer:
2 ways:
a) sizeof($urarray) This function is an alias of count()
b) count($urarray)
Interestingly if u just pass a simple var instead of a an array it will return 1.

49. What is the php predefined variable that tells the What types of images that php supports?
Answer: $_SERVER['HTTP_ACCEPT']

50. How can I know that a variable is a number or not using a _JavaScript?
Answer:
function IsNumeric(sText)
{
var ValidChars = "0123456789.";
var IsNumber=true;
var Char;
for (i = 0; i < sText.length && IsNumber == true; i++)
{
Char = sText.charAt(i);
if (ValidChars.indexOf(Char) == -1)
{
IsNumber = false;
}
}
return IsNumber;
}
51. List out some tools through which we can draw E-R diagrams for mysql.
Answer:
Dbdesigner, conceptdraw etc.

52. How can I retrieve values from one database server and store
them in other database server using php?
Answer:
<?php
db_connect($host,$user,$pwd)
{
$host_name=$host;
$user=$user;
$pwd=$pwd;
$link1 = mysql_connect($host_name, $user, $pwd);
if (!$link1) {
die('Could not connect: ' . mysql_error());
}
return($link1);
}
$link1 =db_connect(hostname, username, password);
$im=mysql_select_db("test") or mysql_error();
$result1=mysql_query("select * from student")or mysql_error();
while ($row = mysql_fetch_array($result1)) {
$id=$row["id"];
$name=$row["name"];
$roll=$row["roll"];
}
mysql_close($link1);
$link2 = db_connect(hostname, username, password);
$im1=mysql_select_db("test1") or die(mysql_error());
//$query1="insert into student1('name','roll','address') values($id,$name,$roll)";
$result1=mysql_query("insert into student1 values('$id','$name','$roll')") or die(mysql_error());
echo "<br>"."Executed";
mysql_close($link2);
?>
53. List out the predefined classes in php?
Answer:
Directory
stdClass
__PHP_Incomplete_Class
exception
php_user_filter

54. How can I make a script that can be bilanguage (supports Eglish, German)?
Answer :
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
You can change charset variable in above line in the script to support bilanguage.

55. What are the difference between abstract class and interface?
Abstract class: abstract classes are the class where one or more methods are abstract but not necessarily all method has to be abstract. Abstract methods are the methods, which are declare in its class but not define. The definition of those methods must be in its extending class.
Interface: Interfaces are one type of class where all the methods are abstract. That means all the methods only declared but not defined. All the methods must be define by its implemented class.

56. How can we send mail-using _JavaScript?
Answer:
NO! JavaScript can't email a form! but, there are alternatives to send the form data to an email address.
Try this:
<form action="mailto: you@yourdmainhere.com " method="post" enctype="text/plain" >
FirstName:<input type="text" name="FirstName">
Email:<input type="text" name="Email">
<input type="submit" name="submit" value="Submit">
</form>

57. How can we repair a mysql table?
Answer:
The syntex for repairing a mysql table is
REPAIR TABLENAME, [TABLENAME, ], [Quick],[Extended]
This command will repair the table specified
if the quick is given the mysql will do a repair of only the index tree if the extended is given it will create index row by row
58. What are the advantages of stored procedures, triggers, indexes?
A stored procedure is a set of SQL commands that can be compiled and stored in the server. Once this has been done, clients don't need to keep re-issuing the entire query but can refer to the stored procedure. This provides better overall performance because the query has to be parsed only once, and less information needs to be sent between the server and the client. You can also raise the conceptual level by having libraries of functions in the server. However, stored procedures of course do increase the load on the database server system, as more of the work is done on the server side and less on the client (application) side.
Triggers will also be implemented. A trigger is effectively a type of stored procedure, one that is invoked when a particular event occurs. For example, you can install a stored procedure that is triggered each time a record is deleted from a transaction table and that stored procedure automatically deletes the corresponding customer from a customer table when all his transactions are deleted.
Indexes are used to find rows with specific column values quickly. Without an index, MySQL must begin with the first row and then read through the entire table to find the relevant rows. The larger the table, the more this costs. If the table has an index for the columns in question, MySQL can quickly determine the position to seek to in the middle of the data file without having to look at all the data. If a table has 1,000 rows, this is at least 100 times faster than reading sequentially. If you need to access most of the rows, it is faster to read sequentially, because this minimizes disk seeks.

59. What is the maximum length of a table name, database name, and fieldname in mysql?
Answer:
Database name- 64
Table name -64
Fieldname-64

 

60. How many values can the SET function of mysql takes?
Answer:
Mysql set can take zero or more values but at the maximum it can take 64 values




61. What are the other commands to know the structure of table using mysql commands except explain command?
Answer:
describe table_name;

62. How many tables will create when we create table, what are they?
Answer:
3 tables will create when we create table. They are
The `.frm' file stores the table definition.
The data file has a `.MYD' (MYData) extension.
The index file has a `.MYI' (MYIndex) extension,

63. What is the purpose of the following files having extensions 1) frm 2) MYD 3) MYI. What these files contains?
Answer:
In MySql, the default table type is MyISAM.
Each MyISAM table is stored on disk in three files. The files have names that begin with the table name and have an extension to indicate the file type.
The `.frm' file stores the table definition.
The data file has a `.MYD' (MYData) extension.
The index file has a `.MYI' (MYIndex) extension,

64. What is maximum size of a database in mysql?
Answer:
If the operating system or filesystem places a limit on the number of files in a directory, MySQL is bound by that constraint.
The efficiency of the operating system in handling large numbers of files in a directory can place a practical limit on the number of tables in a database. If the time required to open a file in the directory increases significantly as the number of files increases, database performance can be adversely affected.
The amount of available disk space limits the number of tables.
MySQL 3.22 had a 4GB (4 gigabyte) limit on table size. With the MyISAM storage engine in MySQL 3.23, the maximum table size was increased to 65536 terabytes (2567 – 1 bytes). With this larger allowed table size, the maximum effective table size for MySQL databases is usually determined by operating system constraints on file sizes, not by MySQL internal limits.
The InnoDB storage engine maintains InnoDB tables within a tablespace that can be created from several files. This allows a table to exceed the maximum individual file size. The tablespace can include raw disk partitions, which allows extremely large tables. The maximum tablespace size is 64TB.
The following table lists some examples of operating system file-size limits. This is only a rough guide and is not intended to be definitive. For the most up-to-date information, be sure to check the documentation specific to your operating system.
Operating System File-size Limit
Linux 2.2-Intel 32-bit 2GB (LFS: 4GB)
Linux 2.4+ (using ext3 filesystem) 4TB
Solaris 9/10 16TB
NetWare w/NSS filesystem 8TB
Win32 w/ FAT/FAT32 2GB/4GB
Win32 w/ NTFS 2TB (possibly larger)
MacOS X w/ HFS+ 2TB

65. Give the syntax of Grant and Revoke commands?
The generic syntax for grant is as following
> GRANT [rights] on [database/s] TO [username@hostname] IDENTIFIED BY [password]
now rights can be
a) All privilages
b) combination of create, drop, select, insert, update and delete etc.
we can grant rights on all databse by usingh *.* or some specific database by database.* or a specific table by database.table_name
username@hotsname can be either username@localhost, username@hostname and username@%
where hostname is any valid hostname and % represents any name, the *.* any condition
password is simply the password of user
The generic syntax for revoke is as following
> REVOKE [rights] on [database/s] FROM [username@hostname]
now rights can be as explained above
a) All privilages
b) combination of create, drop, select, insert, update and delete etc.
username@hotsname can be either username@localhost, username@hostname and username@%
where hostname is any valid hostname and % represents any name, the *.* any condition

66. Explain Normalization concept?
The normalization process involves getting our data to conform to three progressive normal forms, and a higher level of normalization cannot be achieved until the previous levels have been achieved (there are actually five normal forms, but the last two are mainly academic and will not be discussed).
First Normal Form
The First Normal Form (or 1NF) involves removal of redundant data from horizontal rows. We want to ensure that there is no duplication of data in a given row, and that every column stores the least amount of information possible (making the field atomic).
Second Normal Form
Where the First Normal Form deals with redundancy of data across a horizontal row, Second Normal Form (or 2NF) deals with redundancy of data in vertical columns. As stated earlier, the normal forms are progressive, so to achieve Second Normal Form, your tables must already be in First Normal Form.
Third Normal Form
I have a confession to make; I do not often use Third Normal Form. In Third Normal Form we are looking for data in our tables that is not fully dependant on the primary key, but dependant on another value in the table

67. How can we find the number of rows in a table using mysql?
Answer: Use this for mysql
>SELECT COUNT(*) FROM table_name;
but if u r particular about no of rows with some special result
do this
>SELECT [colms],COUNT(*) FROM table_name [where u put conditions];

68. How can we find the number of rows in a result set using php?
Answer: for PHP
$result = mysql_query($any_valid_sql, $database_link);
$num_rows = mysql_num_rows($result);
echo “$num_rows rows found”;

69. How many ways we can we find the current date using mysql?
Answer:
SELECT CURDATE();
CURRENT_DATE() = CURDATE()
for time use
SELECT CURTIME();
CURRENT_TIME() = CURTIME()

70. What are the advantages and disadvantages of CASCADE STYLE SHEETS?
External Style Sheets
Advantages
Can control styles for multiple documents at once
Classes can be created for use on multiple HTML element types in many documents
Selector and grouping methods can be used to apply styles under complex contexts
Disadvantages
An extra download is required to import style information for each document
The rendering of the document may be delayed until the external style sheet is loaded
Becomes slightly unwieldy for small quantities of style definitions
Embedded Style Sheets
Advantages
Classes can be created for use on multiple tag types in the document
Selector and grouping methods can be used to apply styles under complex contexts
No additional downloads necessary to receive style information
Disadvantages
This method can not control styles for multiple documents at once
Inline Styles
Advantages
Useful for small quantities of style definitions
Can override other style specification methods at the local level so only exceptions need to be listed in conjunction with other style methods
Disadvantages
Does not distance style information from content (a main goal of SGML/HTML)
Can not control styles for multiple documents at once
Author can not create or control classes of elements to control multiple element types within the document
Selector grouping methods can not be used to create complex element addressing scenarios

71. What type of inheritance that php supports?
Answer: In PHP an extended class is always dependent on a single base class, that is, multiple inheritance is not supported. Classes are extended using the keyword 'extends'.
Usage:
<?php classNamedCartextendsCart{
var $owner; function set_owner ($name) { $this->owner = $name; } } ?>
72. How can increase the performance of mysql select query?
The structure of table view buyers is as follows
+----------------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------------+-------------+------+-----+---------+----------------+
| user_pri_id | int(15) | | PRI | NULL | auto_increment |
| userid | varchar(10) | YES | | NULL | |
+----------------+-------------+------+-----+---------+----------------+
the value of user_pri_id the last row 2345 then What will happen in
the following conditions
Condition1: Delete all the rows and insert another row then What is
the starting value for this auto incremented field user_pri_id ,
Condition2: Delete the last row(having the field value 2345) and
insert another row then What is the value for this auto incremented
field user_pri_id
Answer:
In general, when you want to make a slow SELECT ... WHERE query faster, the first thing to check is whether you can add an index. All references between different tables should usually be done with indexes. You can use the EXPLAIN statement to determine which indexes are used for a SELECT. See section 7.4.5 How MySQL Uses Indexes and section 7.2.1 EXPLAIN Syntax (Get Information About a SELECT).
Some general tips for speeding up queries on MyISAM tables:
To help MySQL optimize queries better, use ANALYZE TABLE or run myisamchk --analyze on a table after it has been loaded with data. This updates a value for each index part that indicates the average number of rows that have the same value. (For unique indexes, this is always 1.) MySQL will use this to decide which index to choose when you join two tables based on a non-constant expression. You can check the result from the table analysis by using SHOW INDEX FROM tbl_name and examining the Cardinality value. myisamchk --description --verbose shows index distribution information.
To sort an index and data according to an index, use myisamchk --sort-index --sort-records=1 (if you want to sort on index 1). This is a good way to make queries faster if you have a unique index from which you want to read all records in order
according to the index. Note that the first time you sort a large table this way, it may take a long time.
In both cases let the value for auto increment field be n then next row will have value n+1 i.e. 2346

73. What are the advantages/disadvantages of mysql and php?
Answer:
Both of them are open source software (so free of cost), support cross platform. php is faster then ASP and JSP.

74. What is the difference between GROUP BY and ORDER BY in Sql?
Answer:
To sort a result, use an ORDER BY clause.
The most general way to satisfy a GROUP BY clause is to scan the whole table and create a new temporary table where all rows from each group are consecutive, and then use this temporary table to discover groups and apply aggregate functions (if any).
ORDER BY [col1],[col2],…,[coln]; Tels DBMS according to what columns it should sort the result. If two rows will hawe the same value in col1 it will try to sort them according to col2 and so on.
GROUP BY [col1],[col2],…,[coln]; Tels DBMS to group results with same value of column col1. You can use COUNT(col1), SUM(col1), AVG(col1) with it, if you want to count all items in group, sum all values or view average

75. What is the difference between char and varchar data types?
Answer:
char(M) M bytes 0<=M<=255
varchar(M) L+1 bytes where L<=M & 0<=M<=255
i.e.; char data type allocate memory statically
and varchar data type allocate memory dynamically

 

76. What is the functionality of md5 function in php?
Answer:
string md5(string)
Calculate the md5 hash of a string. The hash is a 32-character hexadecimal number. We can use it to generate keys, which we use to identify users etc. If we add random no techniques to it the md5 generated now will be totally different for the same string we are using..

77. How can I load data from a text file into a table?
Answer:
The mysql provides a LOAD DATA INFILE syntax. U can load data from a file. Gr8 tool but u need to make sure that
a) data is delimited
b) u match the colms and data correctly
dont use w/out first learning the syntax

78. How can we know the number of days between two given dates using mysql?
Answer:
select DIFFDATE( NOW(), ‘yyyy-mm-dd’ );

79. How can we know the number of days between two given dates using php?
Answer:
<?php
$tomorrow = mktime(0, 0, 0, date("m") , date("d")+1, date("Y"));
$lastmonth = mktime(0, 0, 0, date("m")-1, date("d"), date("Y"));
echo ($tomorrow-$lastmonth)/86400;
?>

80. How can we change the name of a column of a table?
Answer:
MySQL query to rename table: RENAME TABLE tbl_name TO new_tbl_name
[, tbl_name2 TO new_tbl_name2] ...
or,
ALTER TABLE tableName CHANGE OldName newName.




81. How can we change the name and data type of a column of a table?
Answer:
ALTER [IGNORE] TABLE tbl_name
alter_specification [, alter_specification] | CHANGE [COLUMN] old_col_name column_definition
[FIRST|AFTER col_name]

82. What are the differences between drop a table and truncate a table?
Answer: Delete a Table or DatabaseTo delete a table (the table structure, attributes, and indexes will also be deleted).
What if we only want to get rid of the data inside a table, and not the table itself? Use the TRUNCATE TABLE command (deletes only the data inside the table).

83. When you want to show some part of a text displayed on an HTML page in red font color, what different possibilities are there to do this? What are the advantages/disadvantages of these methods?
Answer:
Using Html font color tag:
<font color=RED> I am Amin </font>
Using tag in CSS:
STRONG {color:red}
So when we use the <STRONG> tag:
I am <STRONG>Amin</STRONG> about this.
Using Class in CSS:
.colorclass
{
color:#FF3399;
font-weight:900;
}
I am <SPAN CLASS="colorclass">Amin</SPAN>
If we use html the modification will be trouble some because we have to change the code of the page. But when we use CSS then it will be easy to change the CSS file and we can get the desired out put.

84. When viewing an HTML page in a Browser, the Browser often keeps this page in its cache. What can be possible advantages/disadvantages of page caching? How can you prevent caching of a certain page (please give several alternate solutions)?
Answer:
When you use the <HTTP-EQUIV="PRAGMA" CONTENT="NO-CACHE"> metatag in the
header section at the beginning of an HTML Web page, the Web page may
still be cached in the Temporary Internet Files folder.
A page that Internet Explorer is browsing is not cached until half of the 64 KB
> buffer is filled. Usually, metatags are inserted in the header section of an
> HTML document, which appears at the beginning of the document. When the HTML code is parsed, it is read from top to bottom. When the
<HTTP-EQUIV="PRAGMA"
CONTENT="NO-CACHE"> metatag is read, Internet Explorer looks for the
existence of the page in cache at that exact moment. If it is there, it is removed. To properly prevent the Web page from appearing in the cache, place another header section at the end of the HTML ocument. For example:
</BODY>
<HEAD>
<META HTTP-EQUIV="PRAGMA" CONTENT="NO-CACHE">
</HEAD>
</HTML>

85. What are the different methods of passing data or information between two calls of a web page? What are the advantages/disadvantages of these methods?
86. An Apache web server is running on a Linux system. Suddenly, the web server delivers the pages very slow. How could you find out possible reasons for that (when using system commands, please specify their names)?

87. What are the different ways to login to a remote server? Explain the means, advantages and disadvantages?
Answer:
There is at least 3 ways to logon to a remote server:
Use ssh or telnet if you concern with security
You can also use rlogin to logon to a remote server.

88. Please give a regular _expression (preferably Perl/PREG style), which can be used to identify the URL from within a HTML link tag. Example: The regular _expression should match the tag <A HREF="http://www.yoursite.com/" and give the URL ("http://www.yoursite.com/") as a return result. Tags should also be matched if they contain other attributes than the HREF attribute.
Answer:
$regexp = "/[http]+[0-9A-Za-z_:/.]+[^"]/";
$str = "<a HREF="http://www.yoursite.com/"";
preg_match($regexp,$str,$arr);
echo $arr[0];

89. A select query over a large table runs very slow because of the growing number of entries in that table. What different measures could be taken to improve speed?
Answer:
In general, when you want to make a slow SELECT … WHERE query faster, the first thing to check is whether you can add an index. All references between different tables should usually be done with indexes. You can use the EXPLAIN statement to determine which indexes are used for a SELECT.
Some general tips for speeding up queries on MyISAM tables:
A: To help MySQL better optimize queries, use ANALYZE TABLE or run myisamchk --analyze on a table after it has been loaded with data. This updates a value for each index part that indicates the average number of rows that have the same value. (For unique indexes, this is always 1.) MySQL uses this to decide which index to choose when you join two tables based on a non-constant expression. You can check the result from the table analysis by using SHOW INDEX FROM tbl_name and examining the Cardinality value. myisamchk --description --verbose shows index distribution information.

90. A company wants to store their invoices in a database. They already have their customers and articles in that database. Both customer and article are each identified by an unique integer value. Please create the SQL statements for creating the necessary table(s) for storing the invoices in a MySQL database. An invoice should hold information like invoice number, customer, date, article(s) and quantity etc.
Ans:
CREATE TABLE invoice (
id int(11) NOT NULL default '0',
invoceNo int(11) NOT NULL default '0',
customer_id varchar(20) NOT NULL default '0',
article_id varchar(20) NOT NULL default '0',
date varchar(20) NOT NULL default '0',
quantity int(11) NOT NULL default '0',
PRIMARY KEY (id)
) TYPE=MyISAM;

91. For the database from the previous question, please give an SQL query which returns the invoice number of all invoices which contain the article with the number "1234". The query should be able to run under a MySQL 4.0 database.
Answer:
Select invoceNo from invoice where article_id=1234;

92. How would you backup and restore a big MySQL database? What are the advantages of the approach which you have taken over the others?
Use the mysqldump command.

If you have Telnet/SSH access to your MySQL server, log in and issue the following command for each database you want to back up:
shell> mysqldump -u user -ppassword --opt -full database_name > backupfile.sql
Then move the resulting file(s) to your preferred backup areas. If you require more information on the mysqldump command, then simply check out this URL:www.mysql.com/documentation/mysql
Copy all the relevant table files.
If the server isn't updating anything (or you've deliberately killed mysqld for this purpose) then you can copy all the files with the following extensions in your MySQL data directory:
*.frm
*.myd
*.myi
Make sure you restart the MySQL daemon once you finish copying and downloading the files to your preferred backup areas.
TIP: once you've completed the backup, restart MySQL with the --log-update switch. This will allow you to keep track of all modifications done in the MySQL tables since your last 'dump'.
To restore your dumps, you should either restore to an existing database or create a new database using
shell> mysqladmin create database_name
then issue the following command :
shell> mysql -u user -ppassword database_name < backup-file.sql
If you don't have access to Telnet/SSH and you're unable to do backups using the methods described above, you should ask your host if it is possible for them to do a backup for you and put the backups in a separate directory so that you can easily
FTP your backups to your selected backup areas. Otherwise, if you have access to phpMyAdmin, you can use the following procedure:
Access phpMyAdmin, and select the database you wish to 'dump' (backup).
Scroll down and you will see a bulleted point saying: "View dump (schema) of database" along with some radio and check boxes. Choose 'Structure and data', then click on 'Add Drop Table' and 'Send' and click 'Go'. This will save the 'dump' to your hard drive.
To restore a dump using phpMyAdmin, simply insert the file in the correct place once you have chosen the correct database by doing the following:
Choose the database you will insert your data into, or create a new database.
Insert the appropriate SQL queries you already have, or just paste the name of the .sql file you have on your hard drive into the text box under 'Location of the textfile', and fire away!
Tip : use a crontab job to schedule backups periodically.
The advantages of this approach is the backup is only a file consisting of SQL query. So that needs minimum spaces to backup a large database.

93. Create a PHP web script with the following attributes: on start, three HTML form elements are shown: an string input field, a checkbox field, a dropdown/pull down list with 5 elements and a submit button. On submission, the form should be redisplayed (while remaining all options/inputs as the user has selected/entered them). Additionally,
the selections/inputs of the user should be displayed in text. Please solve this without the use of any external libraries.

Answer:
Ans:
<?
$name=$_POST['txtName']; //Value of text field
$chkState=$_POST['chkState']; // Value of check box
$sltItem=$_POST['sltItem']; // Value of the List box
?>
<form name="form1" method="post" action="">
<table width="100%" border="0">
<tr>
<td> <input name="txtName" type="text" id="txtName" value=<? echo $name ?>></td>
</tr> <tr>
<td><input name="chkState" type="checkbox" <? if($chkState=='on') echo "checked" ?> ></td>
</tr><tr>
<td><div align="right"></div>
<select name="sltItem" id="sltItem">
<?
$arr=array("BD","AU","USA","UK","JP"); //Array of the Items os list box
for($i=0;$i<5;$i++){ // 5 items are taken as sample
if($sltItem==$i)
echo" <option value=$i selected >$arr[$i] </option>";
else
echo" <option value=$i>$arr[$i] </option>";
}
?>
</select></td>
</tr><tr>
<td><input type="submit" name="Submit" value="Submit"> </td>
</tr> </table>
</form>

94. What is meant by MIME?
Answer:
Multipurpose Internet Mail Extensions.
WWW's ability to recognise and handle files of different types is largely dependent on the use of the MIME (Multipurpose Internet Mail Extensions) standard. The standard provides for a system of registration of file types with information about the applications needed to process them. This information is incorporated into Web server and browser software, and enables the automatic recognition and display of registered file types. ...

95. What is meant by PEAR in php?
Answer:
PEAR is short for “PHP Extension and Application Repository” and is pronounced just like the fruit. The purpose of PEAR is to provide:
A structured library of open-sourced code for PHP users
A system for code distribution and package maintenance
A standard style for code written in PHP
The PHP Foundation Classes (PFC),
The PHP Extension Community Library (PECL),
A web site, mailing lists and download mirrors to support the PHP/PEAR community
PEAR is a community-driven project with the PEAR Group as the governing body. The project has been founded by Stig S. Bakken in 1999 and quite a lot of people have joined the project since then.
http://pear.php.net/manual/en/introduction.php

96. How can I use the COM components in php?
Answer:
The COM class provides a framework to integrate (D)COM components into your PHP scripts.
string COM::COM ( string module_name [, string server_name [, int codepage]])
COM class constructor. Parameters:
module_name
name or class-id of the requested component.
server_name
name of the DCOM server from which the component should be fetched. If NULL, localhost is assumed. To allow DCOM com.allow_dcom has to be set to TRUE in php.ini.
codepage
specifies the codepage that is used to convert php-strings to unicode-strings and vice versa. Possible values are CP_ACP, CP_MACCP, CP_OEMCP, CP_SYMBOL, CP_THREAD_ACP, CP_UTF7 and CP_UTF8.
Usage:
<?php // starting word $word = new COM("word.application") or die("Unable to instanciate Word"); echo "Loaded Word, version {$word->Version}n"; //bring it to front $word->Visible = 1; //open an empty document $word->Documents->Add(); //do some weird stuff $word->Selection->TypeText("This is a test..."); $word->Documents[1]->SaveAs("Useless test.doc"); //closing word $word->Quit(); //free the object $word->Release(); $word = null; ?>

97. How can I load the dll’s dynamically?

98. How many ways we can give the output to a browser?

Answer:
HTML output
PHP, ASP, JSP, Servlet Function
Script Language output Function
Different Type of embedded Package to output to a browser

99. How can we know that a session is started or not?
Answer:
a session starts by session_start()function.
this session_start() is always declared in header portion.it always declares first.then we write session_register().

100. What is the default session time in php and how can I change it?
Answer:
The default session time in php is until closing of browser




101. What changes I have to done in php.ini file for file uploading?
Answer:
Make the following Line uncomment like:
; Whether to allow HTTP file uploads.
file_uploads = On
; Temporary directory for HTTP uploaded files (will use system default if not
; specified).
upload_tmp_dir = C:apache2triadtemp
; Maximum allowed size for uploaded files.
upload_max_filesize = 2M

102. What are the differences between mysql_fetch_array(), mysql_fetch_object(), mysql_fetch_row()?
Answer:
mysql_fetch_array -- Fetch a result row as an associative array, a numeric array, or both.
mysql_fetch_object ( resource result )
Returns an object with properties that correspond to the fetched row and moves the internal data pointer ahead. Returns an object with properties that correspond to the fetched row, or FALSE if there are no more rows
mysql_fetch_row() fetches one row of data from the result associated with the specified result identifier. The row is returned as an array. Each result column is stored in an array offset, starting at offset 0.

103. How can I set a cron and how can I execute it in Unix, Linux, and windows?
Answer:
Cron is very simply a Linux module that allows you to run commands at predetermined times or intervals. In Windows, it’s called Scheduled Tasks. The name Cron is in fact derived from the same word from which we get the word chronology, which means order of time.
The easiest way to use crontab is via the crontab command.
# crontab –e
This command ‘edits’ the crontab. Upon employing this command, you will be able to enter the commands that you wish to run. My version of Linux uses the text editor vi. You can find information on using vi here.
The syntax of this file is very important – if you get it wrong, your crontab will not function properly. The syntax of the file should be as follows:
minutes hours day_of_month month day_of_week command
All the variables, with the exception of the command itself, are numerical constants. In addition to an asterisk (*), which is a wildcard that allows any value, the ranges permitted for each field are as follows:
Minutes: 0-59
Hours: 0-23
Day_of_month: 1-31
Month: 1-12
Weekday: 0-6
We can also include multiple values for each entry, simply by separating each value with a comma.
command can be any shell command and, as we will see momentarily, can also be used to execute a Web document such as a PHP file.
So, if we want to run a script every Tuesday morning at 8:15 AM, our mycronjob file will contain the following content on a single line:
15 8 * * 2 /path/to/scriptname
This all seems simple enough, right? Not so fast! If you try to run a PHP script in this manner, nothing will happen (barring very special configurations that have PHP compiled as an executable, as opposed to an Apache module). The reason is that, in order for PHP to be parsed, it needs to be passed through Apache. In other words, the page needs to be called via a browser or other means of retrieving Web content.
For our purposes, I’ll assume that your server configuration includes wget, as is the case with most default configurations. To test your configuration, log in to shell. If you’re using an RPM-based system (e.g. Redhat or Mandrake), type the following:
# wget --help
If you are greeted with a wget package identification, it is installed in your system.
You could execute the PHP by invoking wget on the URL to the page, like so:
# wget http://www.example.com/file.php
Now, let’s go back to the mailstock.php file we created in the first part of this article. We saved it in our document root, so it should be accessible via the Internet. Remember that we wanted it to run at 4PM Eastern time, and send you your precious closing bell report? Since I’m located in the Eastern timezone, we can go ahead and set up our crontab to use 4:00, but if you live elsewhere, you might have to compensate for the time difference when setting this value.
This is what my crontab will look like:
0 4 * * 1,2,3,4,5 wget http://www.example.com/mailstock.php
104. Steps for the payment gateway processing?
Ans:
An online payment gateway is the interface between your merchant account and your Web site. The online payment gateway allows you to immediately verify credit card transactions and authorize funds on a customer's credit card directly from your Web site. It then passes the transaction off to your merchant bank for processing, commonly referred to as transaction batching

105. How many ways I can register the variables into session?
Answer:
session_register(); $_SESSION[]; $HTTP_SESSION_VARS[];

106. Explain different types of errors in php (i.e. arguments in error reporting function)?
Answer:
Three are three types of errors:
1. Notices: These are trivial, non-critical errors that PHP encounters while executing a script - for example, accessing a variable that has not yet been defined. By default, such errors are not displayed to the user at all - although, as you will see, you can change this default behaviour.
2. Warnings: These are more serious errors - for example, attempting to include() a file which does not exist. By default, these errors are displayed to the user, but they do not result in script termination.
3. Fatal errors: These are critical errors - for example, instantiating an object of a non-existent class, or calling a non-existent function. These errors cause the immediate termination of the script, and PHP's default behaviour is t

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