PHPで配列からキー値を削除するにはどうすればよいですか?

<?php
$array = array("size" => "XL", "color" => "gold");
print_r(array_values($array));
?>

Array
(
    [0] => XL
    [1] => gold
)

<?php
/**
* Get all values from specific key in a multidimensional array
*
* @param $key string
* @param $arr array
* @return null|string|array
*/
function array_value_recursive($key, array $arr){
    $val = array();
    array_walk_recursive($arr, function($v, $k) use($key, &$val){
        if($k == $key) array_push($val, $v);
    });
    return count($val) > 1 ? $val : array_pop($val);
}

$arr = array(
    &#39;foo&#39; => &#39;foo&#39;,
    &#39;bar&#39; => array(
        &#39;baz&#39; => &#39;baz&#39;,
        &#39;candy&#39; => &#39;candy&#39;,
        &#39;vegetable&#39; => array(
            &#39;carrot&#39; => &#39;carrot&#39;,
        )
    ),
    &#39;vegetable&#39; => array(
        &#39;carrot&#39; => &#39;carrot2&#39;,
    ),
    &#39;fruits&#39; => &#39;fruits&#39;,
);

var_dump(array_value_recursive(&#39;carrot&#39;, $arr)); // array(2) { [0]=> string(6) "carrot" [1]=> string(7) "carrot2" }
var_dump(array_value_recursive(&#39;apple&#39;, $arr)); // null
var_dump(array_value_recursive(&#39;baz&#39;, $arr)); // string(3) "baz"
var_dump(array_value_recursive(&#39;candy&#39;, $arr)); // string(5) "candy"
var_dump(array_value_recursive(&#39;pear&#39;, $arr)); // null
?>