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