Zend Framework - An open source, object-oriented web application framework implemented in PHP 5
Kodiak PHP - Kodiak PHP can run any PHP code directly (offline) on your iPad, no need for an internet connection.
Agile Toolkit - Agile Toolkit is a PHP framework for developing Web User Interfaces.
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
CodeIgniter - A Fully Baked PHP Framework
WritePHPOnline.Com - WritePHPOnline.Com is an online site that enables you to write code in PHP and view its output.