is_resource in PHP

is_resource — Finds whether a variable is a resource

Syntax: 
bool is_resource ( mixed $var )

Finds whether the given variable is a resource.
Parameters: 

var

    The variable being evaluated.

Return Values:

Returns TRUE if var is a resource, FALSE otherwise.
Examples:

Example #1 is_resource() example
<?php

$db_link = @mysql_connect('localhost', 'mysql_user', 'mysql_pass');
if (!is_resource($db_link)) {
    die('Can\'t connect : ' . mysql_error());
}

?>