Declare a global variable in PHP

This article demonstrates how to declare a global variable in PHP.

1. Using `$GLOBALS` variable

The recommended solution to declare a global variable is to use the $GLOBALS super variable, which is an associative array of all variables defined in the global scope. You can add your variables to the $GLOBALS super variable and use it like follows:

<?php

function initialize_globals()

{

$GLOBALS["OK"] = 200;

$GLOBALS["CREATED"] = 201;

$GLOBALS["ACCEPTED"] = 202;

$GLOBALS["BAD_REQUEST"] = 400;

$GLOBALS["UNAUTHORIZED"] = 401;

$GLOBALS["FORBIDDEN"] = 403;

}

initialize_globals();

echo $GLOBALS['OK']; // 200

Download Run Code

Note that if a variable is declared outside a function, it has a global scope. In other words, you can access a global variable within a function using the global keyword or access it using the $GLOBALS super global array.

<?php

$success = 200;

function foo() {

global $success;

echo $success, PHP_EOL;

}

function bar() {

echo $GLOBALS['success'], PHP_EOL;

}

foo(); // 200

bar(); // 200

Download Run Code

2. Using class

Alternatively, you can create a Globals class containing references to all variables. A typical implementation of the Globals class would look like below:

<?php

class Globals

{

static $OK = 200;

static $CREATED = 201;

static $ACCEPTED = 202;

static $BAD_REQUEST = 400;

static $UNAUTHORIZED = 401;

static $FORBIDDEN = 403;

}

echo Globals::$OK; // 200

Download Run Code

3. Using `define()` function

Finally, you can use the define() function to define named constants that are accessible throughout the script. The advantage of using this method over all the others is that the constant value cannot be modified once it has been created. The following example provides an illustration.

<?php

define("OK", 200);

define("CREATED", 201);

define("ACCEPTED", 202);

define("BAD_REQUEST", 400);

define("UNAUTHORIZED", 401);

define("FORBIDDEN", 403);

echo OK; // 200

Download Run Code

That’s all there is to declaring a global variable in PHP.

Declare a global variable in PHP

1. Using $GLOBALS variable

2. Using class

3. Using define() function

Share this:

1. Using `$GLOBALS` variable

3. Using `define()` function