Interview Questions & Answers

Both GET and POST are used to collect data from a form. However, when security is desired $_POST should be used. When the $_ POST variable is used, all variables used are NOT displayed in the URL. Also, they have no restrictions to the length of the variables. GET should be used when the interaction with the form is more like a question. For e.g. firing a query etc. POST should be used more often when the interaction is more like an order or the interaction changes the state of the resource.
POST example:
Name:
Age:
On clicking submit the URL resembles to: http://www.mysamplesite.com/sample.php
The sample.php file can be used for catching the form data using $_POST
Hello <?php echo $_POST["name"]; ?>.
You are <?php echo $_POST["age"]; ?> years old!
GET EXAMPLE
Name:
Age:
On clicking submit the URL resembles to : http://www.mysamplesite.com/sample.php?name=jim&age=37
The sample.php file can be used for catching the form data using $_GET
Hello <?php echo $_GET["name"]; ?>.
You are <?php echo $_GET["age"]; ?> years old!

CRYPT()
MD5()

mysql_fetch_array - Fetch a result row as an associative array, a numeric array, or both
mysql_fetch_assoc - Fetch a result row as an associative array
mysql_fetch_object - Fetch a result row as an object
mysql_fetch_row —- Get a result row as an enumerated array

Via define() directive, like define ("MYCONSTANT", 100);

By utilizing the com_load and the dotnet_load respectively
you can incorporate COM objects and .NET libraries into your
PHP code, thus anytime you see "library code" in a question,
make sure you remember these two functions.
com_load — Creates a new reference to a COM component [deprecated]
Deprecated, use the OO syntax instead.
<?php
// do this
$obj = new COM($module);
// instead of this:
$obj = com_load($module);
?>

2 ways:
a) sizeof($array_name) - This function is an alias of count()
b) count($array_name) - This function returns the number of elements in an array.
Interestingly if you just pass a simple var instead of an array, count() will return 1.

To know the image size use getimagesize() function
To know the image width use imagesx() function
To know the image height use imagesy() function

The output is displayed directly to the browser.

Using session_id() function, the current value of the session can be found.
Syntax:
String session_id(string $id);

By the use of void set_time_limit(int seconds)
Set the number of seconds a script is allowed to run. If this is reached, the script returns a fatal error. The default limit is 30 seconds or, if it exists, the max_execution_time value defined in the php.ini. If seconds is set to zero, no time limit is imposed.
When called, set_time_limit() restarts the timeout counter from zero. In other words, if the timeout is the default 30 seconds, and 25 seconds into script execution a call such as set_time_limit(20) is made, the script will run for a total of 45 seconds before timing out.

Here is how can you find the number of rows in a result set in PHP:
$result = mysql_query($any_valid_sql, $database_link);
$num_rows = mysql_num_rows($result);
echo "$num_rows rows found";

Different methods to pass data from one web page to another:
1. Store the data in a session variable. By storing the data, the data can be passed from one page to another.
2. Store data in a cookie: By storing data in a persistent cookie, data can be passed from one form to another.
3. Set the data in a hidden field and post the data using a submit button.

Using session_id() function, the current value of the session can be found.
Syntax:
String session_id(string $id)

setcookie('variable','value','time');
variable - name of the cookie variable
value - value of the cookie variable
time - expiry time
Example: setcookie('Test',$i,time()+3600);
Test - cookie variable name
$i - value of the variable 'Test'
time()+3600 - denotes that the cookie will expire after an one hour

Syntax:

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().

User names and passwords in PHP can be encrypted using md5 function.
MD5 function calculates the md5 hash of a string. It is basically used for encryption. It is also used for digital signature applications, where a large file must be "compressed" in a secure manner.
Example:
Md5($str);
Crypt() function can also be used to encrypt a string,. It used MD5, DES or blow fish algorithms for encryption.
Syntax:
Crypt(str, salt)
Salt is an optional parameter used to increase the number of characters encoded, to make the encoding more secure

session_unset() function frees all session variables currently registered.
If $_SESSION (or $HTTP_SESSION_VARS for PHP 4.0.6 or less) is used, use unset() to unregister a session variable.
i.e. unset ($_SESSION['varname']);.

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];

$text = "mailto:info@abc.com?subject=Feedback";
preg_match('|.*@([^?]*)|', $text, $output);
echo $output[1];
Note that the second index of $output, $output[1], gives the match, not the first one, $output[0].