PHP

Documentation

• PHP Manual

Best Practices

• PHP The Right Way
• PHP Best Practices: A short, practical guide for common and confusing PHP tasks

Security

• The 2018 Guide to Building Secure PHP Software

Debugging

• Xdebug

Standard PHP Library (SPL)

TODO

PHP Types

• PHP type comparison tables
• Type Juggling

Unicode / UTF-8

If you aren't using a framework you probably need to be using the mb_* variants of string functions. Also watch out for databases storing string in encoding different from UTF-8.

See https://phptherightway.com/#php_and_utf8

Misc

• If you get a blank SOD, enable display of errors in php.ini. The location depends on the installation and web server but usually: /etc/php/X.Y/apache2/php.ini where X.Y is the PHP version.