Kodiak PHP - Kodiak PHP can run any PHP code directly (offline) on your iPad, no need for an internet connection.
WritePHPOnline.Com - WritePHPOnline.Com is an online site that enables you to write code in PHP and view its output.
Coder - The Cloud IDE, Solved
PHPTester.net - PHPTester.net gives developers and learners the ability to write their PHP code and get the output online.
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
Rapid PHP - Rapid PHP editor is the world's fastest and lightest PHP IDE for Windows with code intelligence and tools for PHP, HTML, CSS, and JavaScript, including PHP debugger, FTP/SFTP client, UTF-8 support and more.