PHP で配列キーの先頭に文字列を効率的に追加するにはどうすればよいですか?

<code class="php">$prefix = "prefix";
$array = array_combine(
    array_map(fn($k) => $prefix . $k, array_keys($array)),
    $array
);</code>

<code class="php">$prefix = "prefix";
foreach ($array as $k => $v) {
    $array[$prefix . $k] = $v;
    unset($array[$k]);
}</code>

<code class="php">class KeyPrefixer {
    private $prefix;
    public function __construct($prefix) {
        $this->prefix = (string)$prefix;       
    }
    public static function prefix(array $array, $prefix) {
        $prefixer = new KeyPrefixer($prefix);
        return $prefixer->mapArray($array);
    }
    public function mapArray(array $array) {
        return array_combine(
            array_map(array($this, 'mapKey', array_keys($array)),
            $array
        );
    }
    public function mapKey($key) {
        return $this->prefix . (string)$key;
    }
}</code>