Types: string, int, float, bool, array, null
Constants: predefined constants, magic constants
Predefined variables: $http_response_header, $argc, $argv
Superglobals: $GLOBALS, $_SERVER, $_GET, $_POST, $_FILES, $_COOKIE, $_SESSION, $_REQUEST, $_ENV
Operators: precedence, arithmetic, comparison, logic, array
Control structures: if-elseif-else, for, foreach, while, do-while, switch, break, continue, match
Require/include: require, include, require_once, include_once, include_path, set_include_path
Functions: all A-Z, by task/area/extension, defining, args, named args, return, variable function names
Classes: constructors, properties, class constants, visibility, inheritance, autoloading
Exceptions: try, catch, throw, finally, user defined exceptions