Practice exercise -- Tokens: basic elements of PHP Special symbols: mathematical: + - * / % punctuation: . ; ? , logical: <= == != >= (two-character symbols) other: ( ) { } [ ] blank ... Word symbols: reserved words or keywords (lowercase) do, echo, else, elseif, false, for, if, print, switch, true, while, ... Identifiers: names of things that appear in a program such as variables, functions, and classes; they are preceded by a dollar sign ($) and consist of letters, digits, and the underscore character (_). They should not start with a digit, and are case-sensitive. Indicate whether the following would be classified as a special symbol, word symbol, identifier, or is invalid: Token Special symbol Word Symbol Identifier Invalid -------- -------------- ----------- ---------- ------- + lastName $amount true $3D $PI != one Way Print LAB_FEE $fixed-cost