array_keys Return all the keys of an array Description arrayarray_keys arrayinput mixedsearch_value boolstrict array_keys returns the keys, numeric and string, from the input array. If the optional search_value is specified, then only the keys for that value are returned. Otherwise, all the keys from the input are returned. As of PHP 5, you can use strict parameter for comparison including type (===). <function>array_keys</function> example 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.outputs; 0 [1] => color ) Array ( [0] => 0 [1] => 3 [2] => 4 ) Array ( [0] => color [1] => size ) ]]> See also array_values and array_key_exists.