How to define global functions in PHP

Question

How to define a global function which would be accessible from any page?

Answer 1

You could declare a function inside a function, be careful to call the outside function only once or you'll get an error.

class MyClass {

  function declareGlobalsFn () {
    // functions declared inside a function have global scope

    function globalfn1() {echo "fn1";}

    function globalfn2() {echo "fn2";}
  }
}

$ob = new MyClass();
$ob->declareGlobalsFn();

globalfn1(); // fn1
globalfn2(); // fn2

Answer 2

If you want your function to always be available, without including it, do this:

1. Create your function in a php file.

2. In your php.ini search for the option auto_prepend_file and add your php file to that line, like this:

   auto_prepend_file = "/path/to/my_superglobal_function.php"

Or if you write it with a non absolute path, like this:

auto_prepend_file = "my_superglobal_function.php"

It will look in your include_path in php.ini to find the file.

Answer 3

Put it in an include, then include it.

Answer 4

In include.php:

function myGlobalFunction() {
    // do someting
}

Then in every page you want to use it:

include 'include.php';
myGlobalFunction();

Answer 5

To expand on luarwo's answer, you can declare the function right in your class constructor. This could make your class a sort of function library, where the functions are accessible from any page where you create your class instance.

Sandbox\MyGameLib

<?php
namespace Sandbox;
class MyGameLib {
    public function __construct() {
        if (!function_exists('loveGame')) {
            function loveGame($game) {
                print "The game $game is awesome";
            }
        }
    }
}

Seesaw

<?php
namespace Seesaw;
use Sandbox\MyGameLib;

$m = new MyGameLib();
loveGame('Tempest');

The game Tempest is awesome

Answer 6

Then in every page you want to use it:

include 'include.php'; myGlobalFunction();

-

Put it in an include, then include it.

This technically may not be correct, depending on the context.

'Page' could be perceived as 'file', Eg "You must include the function's file within each file you want to use the function".

Once a function is defined in your program, it can be accessed from anywhere moving forward up until the program has finished executing.

Say you have this:

index.php:

<?php

function echo_1() {
  echo 1;
}

echo_1();

require 'boot.php';

---

boot.php

<?php

include_once 'page.php';

echo_1();
echo_9342949();

---

page.php

<?php

function echo_9342949() {
  echo 9342949;
}

echo_1();

---

With that, your output would be 1119342949.

Of course, when you say 'page' you may literally mean a directly accessed stand-alone 'page file', in which case the answers from the other users will suffice. However, if you're looking to use the same function from different locations throughout your program, simply define it before you intend to use it and you can access it anywhere moving forward regardless of scope.

Edit:

However, if you're looking to use the same function from different locations throughout your program, simply define it before you intend to use it and you can access it anywhere moving forward regardless of scope.

To correct myself, this of course isn't true for things like class functions, but for normal functions this remains true.