3v4l.org

run code in 300+ PHP versions simultaneously
<?php $headers = array( 'From' => 'webmaster@example.com', 'Reply-To' => 'webmaster@example.com', 'X-Mailer' => 'PHP/' . phpversion(), ); print_r(implode(array_map( function ($v, $k) { return $k . ': ' . $v; }, $headers, array_keys($headers) ), '\r\n'));

preferences:
25.78 ms | 402 KiB | 5 Q