How to Efficiently Add a Prefix to Array Keys in PHP?

Adding a Prefix to Array Keys Efficiently

The imperative question is: How to efficiently add a prefix to the keys of a flat array?

Solution 1: Using PHP >= 7.4 Arrow Functions

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

Solution 2: Using an External Class (PHP < 5.3)

For PHP versions prior to 5.3, the following class-based approach can be used:

<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, $prefix);<h3>Additional Approaches</h3>
<ul><li><strong>Using a Loop (PHP >= 5.3)</strong></li></ul>
<pre class="brush:php;toolbar:false"><code class="php">$prefix = "prefix";
foreach ($array as $k => $v)
{
    $array[$prefix . $k] = $v;
    unset($array[$k]);
}</code>

• Using array_combine() with create_function() (PHP < 5.3)

Not recommended due to security concerns.

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

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