Wie füge ich in PHP effizient ein Präfix zu Array-Schlüsseln hinzu?

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

$prefix = "prefix";
$array = KeyPrefixer::prefix($array, $prefix);<h3>Zusätzliche Ansätze</h3>
<ul><li><strong>Verwendung einer Schleife (PHP >= 5.3)</strong></li></ul>
<pre class="brush:php;toolbar:false"><code class="php">$prefix = "prefix";
foreach ($array as $k => $v)
{
    $array[$prefix . $k] = $v;
    unset($array[$k]);
}</code>

<code class="php">$array = array_combine(
    array_map(create_function('$k', 'return "prefix$k";'), array_keys($array)),
    $array
);</code>