Why global is null in function?

Question

I get this strange problem....

All the page has this code only. global $currentPage; is null and i dont know why...

<?php
$pager = $_PARAMS["this"];
$pages = 5;
$currentPage = 1;
$tst="ap";
$nearPages = 5;
//Prologic
?>
<div class="pager">
<?php
$nearPagesHalf = ($nearPages - 1) / 2;

drawNumbers(1, 1);
if ($currentPage - $nearPagesHalf <= 0) {

}

drawNumbers($pages, $pages);
?> 

    <?php

    function drawNumbers($from, $to) {
        global $currentPage;



        for ($i = $from; $i <= $to; $i++) {

            echo $currentPage;

            if ($i == $currentPage) {
    ?> <span class="pageNumbers current"><?= $i ?></span>

    <?php
            } else {
    ?>
                <a href="#">
                    <span class="pageNumbers"><?= $i ?></span>
                </a>
<?php
            }
        }
?>
    <?php
    }

    function drawDots($from, $to) {

    }
    ?>

</div>

THE PROBLEM

echo $currentPage; prints 1 
        function drawNumbers($from, $to) {
            global $currentPage;
           echo $currentPage; prints nothing

If it is the only code of one page then how this $pager = $_PARAMS["this"]; supposed to work? — zerkms
– zerkms, Commented Nov 2, 2010 at 4:01

Melebius · Accepted Answer · 2021-05-12 10:45:29Z

39

I bet you're executing this code by including this file inside another function.

So you need to mark the first variable occurrence as global too.

Btw, global variables are weird, the more simple and correct way to pass the data to the function is to use function parameters.

edited May 12, 2021 at 10:45

Melebius

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answered Nov 2, 2010 at 4:02

zerkms

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5 Comments

zerkms Over a year ago

@Parhs: then mark the first variable as global too: global $currentPage = 1;. But anyway - this solution is terrible. As well as eval() is terrible.

GorillaApe Over a year ago

I hate globals too but the framework which i am forced to use is composed of many globals!

GorillaApe Over a year ago

@BoltClock each page while executing php is evaled!Is that too bad? I wouldnt do something like that but i cant say exactly why it is bad

zerkms Over a year ago

@Parhs: it is very bad ;-) it is terrible slow, it is difficult to maintain/develop/debug/etc

Valentoni Over a year ago

Global is weird but of course it exists for a reason. I have a case in which i cannot access the global var to pass it through the rest of the system execution using parameters, unless i kick away the design pattern and good practices. The only solution is the global var declaration.

Luke · Accepted Answer · 2010-11-02 04:02:16Z

5

The $currentPage defined at the top does not live in global space. Why don't you just pass the $currentPage as the first parameter to the drawNumbers function? It's much cleaner that way:

drawNumbers( $currentPage, 1, 1 );

function drawNumbers($currentPage, $from, $to) {
// no need define $currentPage here since it's passed
}

answered Nov 2, 2010 at 4:02

Luke

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Comments

Albert · Accepted Answer · 2021-11-19 19:36:36Z

I had a similar problem, but the solution is not on this page so I am putting here in order to help anyone who might show up looking.

My global variable was an object and it worked fine when calling the global vairable from a method AFTER the variable was defined.

class object{

    function __construct($v1, $v2){

    }

    function methodA(){
        global $a;
        var_dump($a);
    }
}
$a = new object($var1, $var2);
$a->methodA(); //Object...

However, when trying to use the global variable before the constructor has return it does not work.

 class object{

    function __construct($v1, $v2){
        $this->methodA();//NULL
    }

    function methodA(){
        global $a;
        var_dump($a);
    }
}
$a = new object($var1, $var2);

This looks like a dunce-cap situation, but my site is a lot more complex than this simplified scenario. So it took me a while to figure out that I was calling it before it was defined.

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