The PHP Manual provides both a functional reference and a language reference along with explanations of PHP's major features. The PHP Manual, unlike most languages' documentation, encourages PHP developers to add their own examples and notes to each page of the documentation. This topic explains contribution to the PHP manual, along with tips, tricks, and guidelines for best practice.
Vim's built-in manual is the authoritative source of information and documentation on every Vim feature, including configurations, built-in functions, and even Vimscript. While not the most beginner-friendly interface, if you know how to look through it, you can find what you need.
Start searching by executing
:help [subject], or