PHP

Topic

Overview

PHP Must Watch A curated list of PHP videos. Everything from design patterns, frameworks, testing and security is covered.
18 Must Watch talks More quality PHP talks.
Immutable Objects Learn about immutable objects in the context of PHP
CLI Debugging Handy tips to get xDebug working from the command line.
PSR7 and HTTP headers A good resource on PSR7 and HTTP headers
Learning OO PHP Tons of resources for learning OO PHP
Objects with __toString are not strings Fun PHP facts from chx :)
Threading Learn about threads in PHP with pthreads

PHP Internals

Topic

Overview

Segmentation Faults Learn the internals of a seg fault in PHP.
Exception Internals Learn the internals of a PHP exception.
PHP Objects & Classes Learn how the Zend engine handles objects and classes
Internals Blog A blog with a variety of posts on PHP internals