Does PHP have an equivalent of C/C++'s #ifdef?

Question

I\'m trying to define a constant, but I don\'t want to redefine it if it\'s already been defined. Here\'s a C sample:

#ifndef BASEPATH
#define BASEPATH /mnt/www         


        

Answer 1

Use defined() function

if(!defined("constantname")) {
   define("constantname", "value");
}