Trying to get 2 plugins to work together

[s22-tech]

I'm trying to get my email-notify plugin to work with the append-qs plugin however the two don't play well together (they work well separately, though).

The email-notify plugin appears to be triggered first, and so never sees the appended querystring. It uses
yourls_add_action('pre_redirect', 's22_email_notification');
to call the function.

append-qs is using
yourls_add_filter('redirect_location', 'append_qs_redirect');
to call it's function.

How can I get Yourls to call append-qs first and then pass it's output to email-notify? I can't find documentation that states the calling order of filters and actions and how they work together.

Thanks,
Marc

[ozh]

You can pass a priority to the filter. See

YOURLS/includes/functions-plugins.php

Line 92 in 8c66db0

function yourls_add_filter( $hook, $function_name, $priority = 10, $accepted_args = NULL, $type = 'filter' ) {

[s22-tech]

OK. I changed append-qs to use
yourls_add_filter('redirect_location', 'append_qs_redirect', 1);
and email-notify to use
yourls_add_action('pre_redirect', 's22_email_notification', 2);
but email-notify is still being called first.

I'm just guessing here, but it appears that actions get called before filters? How do these work together?

[s22-tech]

If I change the filter in append-qs to an action:
yourls_add_action('pre_redirect', 'append_qs_redirect', 1);
it now gets called first.

However, the appended URL is not being passed to email-notify.

[ozh]

3 things :

• Filters and actions are called in the same order as they are encountered in the code.
• the priority parameter is only used when 2 functions are hooked to the same filter or action.
• what the second plugin gets as input parameters depends on what the first plugin returns ...

[s22-tech]

Great info to have. Thanks! But my problem right now is getting the load order correct. I think that may be the source of my other problems.

How do you force one plugin to always load before another one?

[ozh]

The "load order" doesn't matter. The fact that includes/functions-geo.php gets loaded after includes/functions-formatting.php doesn't matter. Similarly, the fact that user/plugins/joe-cool/plugin.php gets loaded before user/plugins/zzz/plugin.php doesn't matter.

All that may matter is, if two functions are hooked to the same filter or action, which one gets triggered first? Here comes the priority parameter.

[s22-tech]

OK, that makes sense since the load order did change after I made them both use the same action as I mentioned above. But I didn't think it was working since the output from append-qs is still not being passed to email-notify.

yourls_add_action('pre_redirect', 'append_qs_redirect', 1);

function append_qs_redirect($url) {
...
	return $url[0].$append_qs;
}

yourls_add_action('pre_redirect', 's22_email_notification', 2);

function s22_email_notification($args) {

	---> How do I retrieve the output of the append-qs plugin here?  <---
...

}

[dgw]

2 comes after 1.

YOURLS/includes/functions-plugins.php

Lines 218 to 219 in 23d21fd

	// Sort filters by priority
	ksort( $yourls_filters[ $hook ] );

[ozh]

Now that you show code, I see the problem. Filters are value modifiers and they return a value. Actions are events. They don't return values.

See here

YOURLS/includes/functions.php

Line 217 in 8c66db0

yourls_do_action( 'pre_redirect', $location, $code );

for instance:
you don't have something like $some_value = yourls_do_action("pre_redirect", $location, $code), it's just the yourls_do_action() part. So the return statement in your plugin function is useless.

So, 2 ways for your problem:

• either hook in a filter, not an action
• or use an action and store somewhere values that are changed and supposed to be used later.

[s22-tech]

I'm sorry, but I don't know what you're trying to say. I thought I had the priorities set correctly.

[dgw]

I misunderstood the problem, sorry.

(btw, you can reply to a thread instead of posting a new top-level answer every time)

[s22-tech]

So how do I retrieve the output of the append-qs plugin in the email-notify plugin?