(PHP4 )

array_keys -- Return all the keys of an array


array array_keys (array input [, mixed search_value])

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

$array = array (0 => 100, "color" => "red");
array_keys ($array);       // returns array (0, "color")

$array = array ("blue", "red", "green", "blue", "blue");
array_keys ($array, "blue");  //  returns array (0, 3, 4) 

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)
            $t[] = $k;
        return $t;

See also array_values().