Kodiak PHP - Kodiak PHP can run any PHP code directly (offline) on your iPad, no need for an internet connection.
PHPCodeChecker - PHPCodeChecker is a best-in-class service that enables developers and PHP programmers to write their code online and analyze it.
CodeLobster PHP Edition - CodeLobster - Free portable PHP IDE with support Drupal, Smarty, Twig, WordPress, Joomla, JQuery, CodeIgniter, HTML, CSS, JavaScript, AngularJS, CakePHP, Facebook, Laravel, Phalcon, Symfony, Yii
PHP Sandbox - PHP Sandbox is one of the major online sites that provides a Development Environment for PHP equipped with a Composer Package.
WritePHPOnline.Com - WritePHPOnline.Com is an online site that enables you to write code in PHP and view its output.
OnlinePHPFunctions - OnlinePHPFunctions is a powerful online code tester that lets you add PHP source code and view its output on your favorite web browser.