Atom - At GitHub, we’re building the text editor we’ve always wanted: hackable to the core, but approachable on the first day without ever touching a config file. We can’t wait to see what you build with 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
PhpStorm - Professional IDE for PHP and Web Developers
Kodiak PHP - Kodiak PHP can run any PHP code directly (offline) on your iPad, no need for an internet connection.
AWS Cloud9 - AWS Cloud9 is a cloud-based integrated development environment (IDE) that lets you write, run, and debug your code with just a browser.
WritePHPOnline.Com - WritePHPOnline.Com is an online site that enables you to write code in PHP and view its output.