Declaring a global variable inside a function

Question

I have two PHP files. In the first I set a cookie based on a $_GET value, and then call a function which then sends this value on to the other file. This is s

Answer 1

This is a simple and working code to initialize global variable from a function :

function doit()
{
    $GLOBALS['val'] = 'bar';
}
doit();
echo $val;

Gives the output as :

bar

Answer 2

The following works.

<?php

    foo();
    bar();

    function foo()
    {
        global $jabberwocky;
        $jabberwocky="Jabberwocky<br>";

        bar();
    }

    function bar()
    {
        global $jabberwocky;
        echo $jabberwocky;
    }

?>

to produce:

Jabberwocky
Jabberwocky

So it seems that a variable first declared as global inside a function and then initalised inside that function acquires global scope.

Answer 3

you have to define the global var in the second function as well..

// global scope
$ref_id = 1;

grabReferral($rid){
   global $ref_id;
   $ref_id = $rid;
}

someOtherFunction(){
    global $ref_id;
    sendValue($ref_id);
}

felix

Answer 4

personally, I would recommend the $GLOBALS super variable.

function foo(){
  $GLOBALS['foobar'] = 'foobar';
}
function bar(){
  echo $GLOBALS['foobar'];
}
foo();
bar();

DEMO

Answer 5

The global keyword lets you access a global variable, not create one. Global variables are the ones created in the outermost scope (i.e. not inside a function or class), and are not accessible inside function unless you declare them with global.

Answer 6

Disclaimer: none of this code was tested, but it definitely gets the point across.

Choose a name for the variable you want to be available in the global scope. Within the function, assign a value to the name index of the $GLOBALS array.

function my_function(){

    //...

    $GLOBALS['myGlobalVariable'] = 42;    //globalize variable

    //...
}

Now when you want to access the variable from code running in the global scope, i.e. NOT within a function, you can simply use $ name to access it, without referencing the $GLOBALS array.

<?php
    //<global scope>

    echo $myGlobalVariable;  //outputs "42"

    //</global scope>
?>

To access your global variable from a non-global scope such as a function or an object, you have two options:

1. Access it through the appropriate index of the $GLOBALS array. Ex: $GLOBALS['myGlobalVariable'] This takes a long time to type, especially if you need to use the global variable multiple times in your non-global scope.

2. A more concise way is to import your global variable into the local scope by using the 'global' statement. After using this statement, you can reference the global variable as though it were a local variable. Changes you make to the variable will be reflected globally.

       //<non global scopes>
       function a(){
           //...
           global $myGlobalVariable;
           echo $myGlobalVariable;    // outputs "42"
           //...
        }
       function b(){
           //...
           echo $GLOBALS['myGlobalVariable'];    // outputs "42"
           echo $myGlobalVariable;               // outputs "" (nothing)
                                                 // ^also generates warning - variable not defined
           //...             
       }
       //</non global scopes>
   

Please use global variables in any language with caution, especially in PHP.

See the following resources for discussion of global variables:

• http://chateau-logic.com/content/dangers-global-variables-revisited-because-php

• http://c2.com/cgi/wiki?GlobalVariablesAreBad