Class variables not correct on page

Question

I'm trying to make some of the variables from my plugin available for an instance of the class on my page. But it's not showing up the correct values.

Here's the relevant part of the plugin:

class opi{
    // version
    public $opi_version = "1.0";

    public $mg = 0;

    //constructor
    public function opi(){
        $this->__construct();
    }

    public function __construct(){
        add_action('init', array(&$this, 'o_check'));
        // ...
    }

    function o_check(){
        if (is_user_logged_in()){
            $this->mg = 4;
        }
    }
}
$opi = new opi;

If I put echo $this->mg; just before the closing brace in the o_check() function, then it shows 4. Fine.

Now if I put the following in page.php, and I'm logged into WordPress, I get the result 0.

<?php $pageopi = new opi; ?>
<?php echo $pageopi->mg; ?>

Any ideas where I'm going wrong please?

Answer 1

When you write that code

<?php $pageopi = new opi; ?>
// 1. object created
// 2. __construct is called
// 3. init action hook is set but is never executed so is o_check method
<?php echo $pageopi->mg; ?>

At this stage, init hook was executed long time before $pageopi is created actually, when page is loaded. init action hook is executed even before page.php start to execute.

Solution:

1. You should use the global $opi; object page.php instead of create new one.

2. Or create a new global object before the init action hook (in plugins_loaded hook) and use it on page.php

Answer 2

Well, you're not executing o_check in your page.php, so the value of mg variable stays at zero.

In your constructor you are adding an action hook, yes, but it will only kick in on the next page refresh. Consider using do_action as well, though I'm not sure if executing one then immediately the other will work.

Answer 3

If you add this part:

<?php $pageopi = new opi; ?>
<?php echo $pageopi->mg; ?>

in a theme template it will initialize the object after the init hook runs and so the o_check method will never run. That is the problem. That is why it works if you initialize beneath the object but not if you initialize in the page template. You need to change hooks, or initialize earlier, or call o_check explicitly.

Initializing your object as a global would work.

class opi{
  // ...
}
global $opi;
$opi = new opi;

Then, in your template you could use:

global $opi;
echo $opi->mg;

Though the way you are using it a static class might as well or better. It is hard to say. I can't tell what the end purpose of the class is.