Making a PHP variable global accross multiple web pages

Question

I'm fairly new to PHP so sorry if this is a naive question, but I want to build a php function library that utilizes a variable that is global across multiple pages. I'm using these 3 files to test:

functions.php

<?php
    function report()
    {
        echo "Value = ".$GLOBALS["var"]; 
    }
?>

index.php

<?php
    $var = "ABC";
    require "functions.php";
    echo "<h1>index.php</h1>";
    report();
?>
<br /><br />
<input type=button onClick="location.href='page2.php'" value="Page2">

page2.php

<?php   
    require "functions.php";
    echo "<h1>page2.php</h1>";
    report();
?>

The report function called by index.php echoes Value = ABC as expected. But when the Page2 button is clicked, the report function called by page2.php displays an Undefined index error raised by $GLOBALS["var"] in functions.php.

I'd like to use $GLOBALS["var"] when it is referenced from page2.php. Can anyone tell me how to enable this? Thanks for any help!

You need [sessions](http://php.net/manual/en/features.sessions.php). $GLOBALS is only global within a script. — , May 24 '15 at 21:20
If you open `page2.php` you don't have `$GLOBALS["var"]` anywhere defined. — Rizier123, May 24 '15 at 21:20
Bingo for `sessions`! I added: `session_start();` at the beginnings of `index.php` and `page2.php` and substituted `$_SESSION['var']` for all the global `var` references. Thanks Hobo Sapiens. — wade, May 24 '15 at 21:49
Rizier123, I'm not sure how to define `$GLOBALS["var"]` in `page2.php` without reintializing it and loosing the original value? — wade, May 24 '15 at 21:51

score 5 · Accepted Answer · edited May 23 '17 at 12:18

5

First of all, here are a few links you should read about $_SESSIONS variables.

I've update your code to make you an example.

functions.php

<?php
function report()
{
    if(isset($_SESSION['var']))
        echo "Value = ". $_SESSION['var']; 
}
?>

index.php

<?php
        session_start();
?>
<html>
<head>
</head>
<body>
    <?php

        $_SESSION['var'] = "ABC";

        require('functions.php');
        echo "<h1>index.php</h1>";

        report();
    ?>
    <br><br>
        <input type="button" onClick="location.href='page2.php'" 
               value="Page2">
</body>

page2.php

<?php 
session_start();
?>
<html>
<head>
</head>
<body>
    <?php
         require ('functions.php');
         echo "<h1>page2.php</h1>";
         report();
     ?>
</body>
</html>

edited May 23 '17 at 12:18

Community

1
1

answered May 24 '15 at 21:50

Falt4rm

915
6
21

actually, placing HTML above `session_start();` is considered as outputting before header, therefore it's best to first declare it `` then followed by ` ...` - Rerences http://php.net/manual/en/function.error-reporting.php and http://stackoverflow.com/questions/8028957/how-to-fix-headers-already-sent-error-in-php – Funk Forty Niner May 24 '15 at 22:05
Ok - seems everyone learned in this topic - I modify then code then. Edit : done. – Falt4rm May 24 '15 at 22:07

score 4 · Answer 2 · answered May 24 '15 at 21:58

Recommended: Declare your variable.. Or use isset() to check if they are declared before referencing them.

Secondly you need to define a session

<?php
function report()
{
    echo "Value = ". **$_SESSION['var']**; 
}
?>

and use in in all your pages :)

ie, for page 1,

<?php
        session_start();

        $_SESSION['var'] = "XYZ";

        require('functions.php');

        report();
    ?>

and fot page2 also,

<?php 
session_start();

require ('functions.php');
report();
?>

Hope it helps :)

Making a PHP variable global accross multiple web pages

2 Answers2