Kodiak PHP - Kodiak PHP can run any PHP code directly (offline) on your iPad, no need for an internet connection.
Online PHP IDE - Online-php.com is a free online IDE for editing files on an FTP server.
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
Nova - Nova is an all-in-one productivity tool. With Nova you can freely choose which components to add to your projects and which you need for productivity, without any pre-set template.
PythonAnywhere - Host, run, and code Python in the cloud: PythonAnywhere
NuSphere PhpEd - PhpED - PHP IDE integrated development environment for developing web sites using PHP, HTML, Perl, JScript and CSS that combines a comfortable editor, debugger, profiler with the MySQl, PostrgeSQL database support based on easy wizards and tutorials.