( 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 its name. I.e. it is
stored in a variable or returned by a function.
This function works also with class constants.
Пример 1. constant() example
echo constant("MAXSIZE"); // same thing as the previous line
See also define(),
defined() and the section on Constants.