Index[SYMBOL] [A] [B] [C] [D] [E] [F] [G] [H] [I] [J] [K] [L] [M] [N] [O] [P] [Q] [R] [S] [T] [U] [V] [W] [X] [Z] validation, HTML form input values array elements dereferencing return values passing by true/false var_dump( ) function variable scope, functions variable variables variables appending assigning case-sensitivity global superglobals heredoc invalid characters isset( ) function register_globals and scope substitution this (OOP) types variable variables version_compare( ) function virtual( ) function |