How to assign global variable value in a function in php?

Question

i need to assign a global variable value by passing it in a function, something like static variable i guess. Here is my code

<?php

//this is old value
$var = "Old Value";

//need to change the value of global variable
assignNewValue($var);
echo $var;

function assignNewValue($data) {
    $data = "New value";
}
?>

After the execution the value of var need to be New Value. Thanks in advance.

You could [return a value](http://php.net/manual/en/functions.returning-values.php) from the function, [pass by reference](http://php.net/manual/en/language.references.pass.php), or set the variable to [global](http://php.net/manual/en/language.variables.scope.php#language.variables.scope.global). — showdev, Sep 09 '16 at 20:23
What you're doing is, passing *a copy* of the variable to the function `assignNewValue()`. Instead, just do this: `function assignNewValue(){ global $var; $var = "New value"; }` — Rajdeep Paul, Sep 09 '16 at 20:26
`i need to assign a global variable` - no, you don't but you will. And your code will suck. Not now, but soon. By suck, I mean that you will shoot your own foot and lose time wondering what the hell just happened. Good luck. — N.B., Sep 09 '16 at 20:44
@N.B. Don't you think it's better to inform the user, as to why global vars are considered bad, more constructively? — Bhargav Rao, Sep 09 '16 at 20:46
@BhargavRao - no. I think it's clear from what I wrote that it's bad. Plus, the guy's probably not mentally challenged, he can ctrl + t and google "global variable bad". — N.B., Sep 09 '16 at 20:50

score 4 · Answer 1 · answered Sep 09 '16 at 20:23

4

<?php

//this is old value
$var = "Old Value";

//need to change the value of global variable
assignNewValue($var);
echo $var;

function assignNewValue(&$data) {
    $data = "New value";
}
?>

I made the argument of assignNewValue a reference to the variable, instead of a copy, with the & syntax.

answered Sep 09 '16 at 20:23

aaronofleonard

2,546
17
23

3

+10 for explaining the crucial *reference* part. You might want to add this reference as well, [http://php.net/manual/en/language.references.php](http://php.net/manual/en/language.references.php). – Rajdeep Paul Sep 09 '16 at 20:32

score 1 · Answer 2 · edited May 23 '17 at 11:48

You can try it in 2 ways, the first:

// global scope
$var = "Old Value";

function assignNewValue($data) {
   global $var;
   $var = "New value";
}

function someOtherFunction(){
    global $var;
    assignNewValue("bla bla bla");
}

or using $GLOBALS: (oficial PHP's documentation: http://php.net/manual/pt_BR/reserved.variables.globals.php)

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

Take a look: Declaring a global variable inside a function

How to assign global variable value in a function in php?

2 Answers2