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.
Example 1. array_keys() example
The printout of the program above will be:
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Note: This function was added to PHP 4, below is an implementation for those still using PHP 3.
Example 2. Implementation of array_keys() for PHP 3 users
function array_keys ($arr, $term="") { $t = array(); while (list($k,$v) = each($arr)) { if ($term && $v != $term) { continue; } $t[] = $k; } return $t; }
See also array_values().