array_keys Return all the keys or a subset of the keys of an array &reftitle.description; arrayarray_keys arrayinput mixedsearch_value boolstrictfalse 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. &reftitle.parameters; input An array containing keys to return. search_value If specified, then only keys containing these values are returned. strict Determines if strict comparison (===) should be used during the search. &reftitle.returnvalues; Returns an array of all the keys in input. &reftitle.changelog; &Version; &Description; 5.0.0 Added the strict parameter. &reftitle.examples; 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 ) ]]> &reftitle.seealso; array_values array_key_exists array_search