SQL Injection Cheat Sheet : Samples are provided to allow reader to get basic idea of a potential SQL Injection attack and almost every section includes a brief information about...
ApiGen : ApiGen is the tool for creating professional API documentation from PHP source code, similar to discontinued phpDocumentor/phpDoc.
regex101 : Free PCRE-based regular expression debugger with real time explanation, error detection and highlighting.
Pimple : Pimple is a small Dependency Injection Container for PHP 5.3 that consists of just one file and one class (about 50 lines of code).
This is a collection of known design patterns and some sample code how to implement them in PHP. Every pattern has a small list of examples (most of them from Zend Framework, Symfony2 or Doctrine2 as I'm most familiar with this software).