(PHP 4, PHP 5, PHP 7, PHP 8)
array_keys — Return all the keys or a subset of the keys of an array
array_keys() returns the keys, numeric and string, from the array.
If a filter_value is specified, then only the keys for that value are returned. Otherwise, all the keys from the array are returned.
arrayAn array containing keys to return.
filter_valueIf specified, then only keys containing this value are returned.
strictDetermines if strict comparison (===) should be used during the search.
Returns an array of all the keys in array.
Example #1 array_keys() example
<?php
$array = array(0 => 100, "color" => "red");
print_r(array_keys($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));
?>The above example will output:
Array ( [0] => 0 [1] => color ) Array ( [0] => 0 [1] => 3 [2] => 4 ) Array ( [0] => color [1] => size )