Interview Questions & Answers

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']);.