PHP Manual . Prev . ... PHP 4 >= 4.0.4) constant -- Returns the value of a constant . mixed constant ( string name) . constant() will return the value of the constant indicated by name . constant() is useful if you need to retrieve the value of a constant, but do not know it's name. i.e. It is stored in a variable or returned by a function. Example 1. constant() example . php define ("MAXSIZE", 100); echo MAXSIZE; echo constant("MAXSIZE"); // same thing as the previous line ?> ...