Kodiak PHP - Kodiak PHP can run any PHP code directly (offline) on your iPad, no need for an internet connection.
Notepad3 - Notepad3 is a fast and light-weight Scintilla-based text editor with syntax highlighting.
Coder - The Cloud IDE, Solved
TED Notepad - TED Notepad is a portable text editor software that deals with a large variety of text processing tools, supplemental text clipboards, high accessibility through hotkeys, and a customizable number of settings and options.
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
Notepad++ - A free source code editor which supports several programming languages running under the MS Windows environment.