These are some of my favorite programming sites.
There is a great compilation of cheat sheets here that is one of my go to locations for quick syntax reminders. The online version links to the documentation for each command as well.
PHP
PHP Official Documentation - This is the official documentation. No more needs to be said.
Composer’s Home Page - Composer is a great tool for helping build sites and is how to use Slim, Twig, and Redbean. Easily add PHPMail, Swiftmail, and other packages with Composer.
Packagist - Lists the packages available through Composer.
Slim micro framework - A miro framework that I am experimenting with.
Twig template engine - a templating engine that works well with Slim.
Redbean - An ORM for database use. I am just exploring this to see how it works. Slim, Twig, and Redbean can be installed at one time with redslim/redslim.