PHP Manual . ... PHP 4 >= 4.0.0) array_keys -- Return all the keys of an array . array array_keys ( array input [, mixed search_value]) . ... Example 1. array_keys() example . array = array (0 => 100, "color" => "red"); print_r(array_keys ($array)); $array = array ("blue", "red", "green", "blue", "blue"); print_r(array_keys ($array, "blue")); $array = array ("color" => array("blue", "red", "green"), "size" => array("small", "medium", "large")); print_r(array_keys ($array)); . ... Example 2. ...