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...
regex101 : Free PCRE-based regular expression debugger with real time explanation, error detection and highlighting.
Email Standards Project : The Email Standards Project is about working with email client developers and the design community to improve web standards support and accessibility ...
WikkaWiki : WikkaWiki is a flexible, standards-compliant and lightweight wiki engine written in PHP, which uses MySQL to store pages.
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).