I am trying to build 2 separate custom plugins for my website when I run into this problem. Both of them are sharing the same kind of a scope, meaning I can't declare a new constant or function with the same name. Is this a known problem and you just have to add prefix? Or is there a better way to move around this?



In PHP, constants are global so they have no scope. Per the PHP Manual:

Like superglobals, the scope of a constant is global. You can access constants anywhere in your script without regard to scope.

There is an exception to this if you are using a PHP Class. You can then tie the constant to that class.

class My_Class
    const BLAH = 'This is a Constant';
print My_Class::BLAH

As for functions they, like constants, are global as well. Per the PHP Manual:

All functions and classes in PHP have the global scope - they can be called outside a function even if they were defined inside and vice versa.

For example, if I have:

function my_func() {
    function my_other_func() {
        // Code

    // More Code

I can call my_other_func() on its own even though it is being defined within my_func().

You can again skirt this using a PHP Class:

class My_Class
   public function echo_hello_world() {

   private function echo_hello() {
       echo 'Hello ';

   private function echo_world() {
       echo 'World!';

$testObj = new My_Class();


However, if classes are overkill, your best bet is to simply namespace everything by appending something unique in front of the names you are currently using. Usually I will append the textdomain I defined for the plugin/theme so my_function() becomes textdomain_my_function().

| improve this answer | |
  • I am working my way between switching to OOP or just stick with procedural programming. Might be a good chance to jump over. – Tree Nguyen Jul 19 '17 at 0:40
  • I'm in the same boat. I started writing a plugin using procedural programming and it's getting way out of hand so I'm looking to flip it to OOP myself. But anything outside a Class needs to be namespaced though. – Cedon Jul 19 '17 at 0:42

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