[wp-hackers] PHP 4/5 Classes and WP filters. $this is not working.

Aaron Harun admin at anthologyoi.com
Fri Jun 13 23:59:03 GMT 2008

In one of my plugins I just noticed that it works great on PHP 5 and
not on PHP 4. I dind't start using classes until PHP 5, but I've
narrowed it down to the $this keyword used in filters. Below you will
find a brief snippet of the scripts involved, please let me know if
you can see why there would be an issue.

The problems I'm having are weird and are specific to my plugin, but
they don't cause PHP errors and go away if I change the filters from
$this to the actual class name. It seems to me that $this is referring
to two different things. One in the contents add_filter and one in the
remove_filter. I tried moving everything inside the first init()
function outside, but it didn't change anything.

My guess is that it has to do with the way the class is being called,
but I'm not sure what part is causing it.



p.s. If anyone is interested, the plugin causing the trouble is the
latest SVN version of
http://wordpress.org/extend/plugins/ajaxd-wordpress/. The problem is
occurring when inline posts are being loaded with AJAX.

p.p.s. I can explain the logic behind what is going on if needed or wanted.

function init() {

	if(count($classes) > 0){ // $classes is just an array of class names.
		foreach($classes as $class){
			$$class = null;
			global $$class;
			$$class = new $class;
		foreach($classes as $class){



$classes[] = 'AWP_inlineposts';

class AWP_inlineposts {

	function init(){
		add_action('awp_ajax_type_post', 'AJAX');

	function awp_live(){
		add_filter('the_content', array($this,'afunction'),-10,1);

	function AJAX($content){

		remove_filter('the_content', array($this,'afunction'),-10,1);

		$response[] = apply_filters('the_content',$content);

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