Getting Started: Introduction; A simple tutorial
Language Reference: Basic syntax; Types; Variables; Constants; Expressions; Operators; Control Structures; Functions; Classes and Objects; Namespaces; Enumerations; Errors; Exceptions; Fibers; Generators; Attributes; References Explained; Predefined Variables; Predefined Exceptions; Predefined Interfaces and Classes; Predefined Attributes; Context options and parameters; Supported Protocols and Wrappers

Security: Introduction; General considerations; Installed as CGI binary; Installed as an Apache module; Session Security; Filesystem Security; Database Security; Error Reporting; User Submitted Data; Hiding PHP; Keeping Current
Features: HTTP authentication with PHP; Cookies; Sessions; Dealing with XForms; Handling file uploads; Using remote files; Connection handling; Persistent Database Connections; Command line usage; Garbage Collection; DTrace Dynamic Tracing

Function Reference: Affecting PHP's Behaviour; Audio Formats Manipulation; Authentication Services; Command Line Specific Extensions; Compression and Archive Extensions; Cryptography Extensions; Database Extensions; Date and Time Related Extensions; File System Related Extensions; Human Language and Character Encoding Support; Image Processing and Generation; Mail Related Extensions; Mathematical Extensions; Non-Text MIME Output; Process Control Extensions; Other Basic Extensions; Other Services; Search Engine Extensions; Server Specific Extensions; Session Extensions; Text Processing; Variable and Type Related Extensions; Web Services; Windows Only Extensions; XML Manipulation; GUI Extensions

PHP Function List

base64 doesn't exist. Closest matches: