array_keys

(PHP 4 >= 4.0.0)

array_keys -- Return all the keys of an array

Description

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) 

$array = array ("color" => array("blue", "red", "green"), "size" => array("small", "medium", "large"));
array_keys ($array);  //  returns array ("color", "size") 
      

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().