Untools : Collection of thinking tools and frameworks to help you solve problems, make decisions and understand systems.
regex101 : Free PCRE-based regular expression debugger with real time explanation, error detection and highlighting.
DesignPatternsPHP : 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 t...
PrePostPrint highlights experimental publications made with free software.
