Title: Pass variable to filter?
Last modified: August 20, 2016

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# Pass variable to filter?

 *  [Driftless](https://wordpress.org/support/users/driftless1/)
 * (@driftless1)
 * [13 years, 3 months ago](https://wordpress.org/support/topic/pass-variable-to-filter/)
 * Writing a function to do a wp_query with a ‘where’ clause:
 *     ```
       function nc_custom_query($my_where_clause){
   
       function nc_dynamic_where( $where = '' ) {
         $where .= $my_where_clause;
         return $where;
       }
   
       add_filter( 'posts_where', 'nc_dynamic_where' );
         $dynamic = new WP_Query( array( 'post_type' => 'my_type', 'orderby' => 'rand', 'posts_per_page' => $number ));
       remove_filter( 'posts_where', 'nc_dynamic_where' );
   
       return $dynamic;
       }
       ```
   
 * Only this does not work…. since the filter funtion `nc_dynamic_where` can only
   accept `$where` and ouput `$where`…
 * So, how do I get the variable `$my_where_clause` into the filter?
 * Caveat: I’m trying to avoid `global`

Viewing 5 replies - 1 through 5 (of 5 total)

 *  Moderator [bcworkz](https://wordpress.org/support/users/bcworkz/)
 * (@bcworkz)
 * [13 years, 3 months ago](https://wordpress.org/support/topic/pass-variable-to-filter/#post-3464662)
 * You can use a closure if using PHP 5.3 or later. If you are distributing your
   code to others, you may want to avoid this technique for a while as there are
   still older versions out and about.
 * You could also use a class object to store data, but IMO, it’s just a glorified
   OOP type of global. But if done properly, it does avoid some of the ugliness 
   brought on by globals.
 * [More Info.](http://wordpress.stackexchange.com/questions/45901/passing-a-parameter-to-filter-and-action-functions)
 *  Thread Starter [Driftless](https://wordpress.org/support/users/driftless1/)
 * (@driftless1)
 * [13 years, 3 months ago](https://wordpress.org/support/topic/pass-variable-to-filter/#post-3464663)
 * Thanks for the link. I’ll play around with those techniques. (Though to be honest,
   I just threw up my hands and went “global” with that bad boy… )
 * **Edit:** Though for closure / anonymous functions – I was under the impression
   they can’t be unregistered as filters…
 *  Moderator [bcworkz](https://wordpress.org/support/users/bcworkz/)
 * (@bcworkz)
 * [13 years, 3 months ago](https://wordpress.org/support/topic/pass-variable-to-filter/#post-3464689)
 * > Though for closure / anonymous functions – I was under the impression they 
   > can’t be unregistered as filters…
 * Hmm. Haven’t heard that one yet, not like I have my finger on the pulse of hard
   core development though, so a rather meaningless comment. Off the top of my head,
   I don’t see why not based on what little I know. I’m curious enough to want to
   setup a little test, but unfortunately I don’t currently have access to my test
   installation. So unless someone else chimes in, it’ll have to remain a mystery
   for a while.
 *  Thread Starter [Driftless](https://wordpress.org/support/users/driftless1/)
 * (@driftless1)
 * [13 years, 3 months ago](https://wordpress.org/support/topic/pass-variable-to-filter/#post-3464690)
 * I could be wront, but it looks like a function gets registered with a unique 
   ID: an spl_object_cache of the function in question (see: _wp_filter_build_unique_id()).
   So, in order to de-register an anonymous function, one would need to ensure the
   remove_filter function call is the exact same…
 * Not sure myself – but I’ve just seen it tossed out a number of times that WP 
   can’t un-register anonymous functions.
 * Anyway, I’ll just play it “safe” and pollute the place with globals for the time
   being.
 *  Moderator [bcworkz](https://wordpress.org/support/users/bcworkz/)
 * (@bcworkz)
 * [13 years, 3 months ago](https://wordpress.org/support/topic/pass-variable-to-filter/#post-3464691)
 * Ah, I see. I’m sure you are right. I just mistook your meaning. I might have 
   said de-registering such a filter is very awkward or difficult rather than you
   simply can’t. End result is the same, I got lost in silly semantics. End result
   is don’t do it that way if you intend on (or someone else may want to) de-registering,
   it’s not worth the trouble. Thanks for clarifying.
 * I don’t think globals are such a crime in any case. Yes, they have issues, and
   we must avoid using them if there’s a _reasonable_ alternate. But creating tricky
   artifices just so we can pat ourselves on the back that we do not use globals
   is a bit of a self deception IMO. WP uses globals all over the place. A few more
   used very thoughtfully is not going to transform the installation into a complete
   mess. (at least no more than it already is 😉 )
 * I’ve no doubt offended many coders who consider their code artful, in which shortcuts
   such as globals are as horrid as a garish inappropriate brushstroke across a 
   painting. I understand, as well as appreciate, and even applaud such an approach.
   But they need to understand not everyone is talented enough, or even sees the
   need for such an approach. As long as my code does what it’s supposed to with
   reasonable efficiency, is well organized, runs cleanly, and is easy to follow
   and maintain, I feel I’ve done my job, with or without globals.

Viewing 5 replies - 1 through 5 (of 5 total)

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## Tags

 * [filter](https://wordpress.org/support/topic-tag/filter/)
 * [var](https://wordpress.org/support/topic-tag/var/)

 * In: [Hacks](https://wordpress.org/support/forum/plugins-and-hacks/hacks/)
 * 5 replies
 * 2 participants
 * Last reply from: [bcworkz](https://wordpress.org/support/users/bcworkz/)
 * Last activity: [13 years, 3 months ago](https://wordpress.org/support/topic/pass-variable-to-filter/#post-3464691)
 * Status: not resolved

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