Title: Adding custom loop to plugin
Last modified: August 20, 2016

---

# Adding custom loop to plugin

 *  [aronjeney](https://wordpress.org/support/users/aronjeney/)
 * (@aronjeney)
 * [13 years, 1 month ago](https://wordpress.org/support/topic/adding-custom-loop-to-plugin/)
 * I am trying to add a custom loop to the “BAW Manual Related Posts” plugin. I 
   believe I need to use apply_filters but am unsure as to how I go about doing 
   so. I’ve included the snippet from the plugin file that allows custom loops as
   well as my custom loop below. Any insight is appreciated. Thanks in advance!
 * Code from plugin file:
    `$list[] = '<li style="' . esc_attr( $style ) . '" class
   ="' . $class . '"><a href="' . esc_url( apply_filters( 'the_permalink', get_permalink(
   $id ) ) ) . '">' . $thumb . '<br />' . apply_filters( 'the_title', get_the_title(
   $id ) ) . '</a></li>';`
 * My custom loop:
 *     ```
       <div class="home-property-item">
       					                        <div class="property-detail-block">
       					                            <div class="property-pic-wrapper">
       					                               <?php
       					                                if ( has_post_thumbnail() )
       					                                {
       					                                    $image_id = get_post_thumbnail_id();
       					                                    $image_url = wp_get_attachment_image_src($image_id,'full-size', true);
   
       					                                    {
       					                                        ?>
       					                                        <a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>">
       					                                        <?php
       					                                    }
       					                                                the_post_thumbnail('property-post-thumb',array(
       					                                                                        'alt'   => trim(strip_tags( get_the_title($post->ID) )),
       					                                                                        'title' => trim(strip_tags( get_the_title($post->ID) ))
       					                                                )); ?>
       					                                    </a>
       					                                    <?php
       					                                }
       					                                ?>
   
       					                                <?php
       					                                $property_status = get_post_meta($post->ID, 'locality_status', true);?>
       					                                    <p class="<?php echo $property_status; ?>">
       					                                        <?php echo $property_status; ?>
       					                                    </p>
       					                            </div>
   
       					                            <h4>
       					                                <a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>">
       					                                    <?php the_title(); ?>
       					                                </a>
       					                            </h4>
   
       					                            <div class="features-wrapper">
       					                                <span class="bed"><div class="value"><?php echo get_post_meta($post->ID, 'locality_property_bedrooms', true); ?></div> <?php _e('Beds') ?></span>
       					                                <span class="bath"><div class="value"><?php echo get_post_meta($post->ID, 'locality_property_bathrooms', true); ?></div> <?php _e('Baths') ?></span>
       					                                <span class="size"><div class="value"><?php echo get_post_meta($post->ID, 'locality_property_size', true); echo "</div> "; theme_unit(); ?></span>
   
       					                                 <div class="price-box">
       					                                    <h5 class="price">
       					                                        <?php
       					                                            theme_currency();
       					                                            echo number_format(intval(get_post_meta($post->ID, 'locality_property_price', true)));
       					                                        ?>
       					                                    </h5>
       					                                </div>
   
       					                            </div>
   
       					                            <div class="learnmore">
       					                                <a class="blue" href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>">LEARN MORE</a>
       					                            </div>
       					                        </div>
       					                    </div>
       ```
   

Viewing 8 replies - 1 through 8 (of 8 total)

 *  Moderator [bcworkz](https://wordpress.org/support/users/bcworkz/)
 * (@bcworkz)
 * [13 years, 1 month ago](https://wordpress.org/support/topic/adding-custom-loop-to-plugin/#post-3638548)
 * You do not use apply_filter(), you look for occurrences of it in code to determine
   where you want to inject content. Once you identify the right filter, your code
   will use add_filter(). In order to use add_filter(), you need to provide a function
   to call when the apply_filter() function fires. You don’t have one yet, and you
   can’t necessarily just wrap template loop code into a function. Filters often
   want a returned value, and your template loop code outputs content, it does not
   build a value to return. One type can be transformed to another, but it’s not
   always a simple transformation.
 * The other issue is your template loop code is macro scale, it outputs a variety
   of content. This is fine, this is the nature of loops. The issue is the plugin
   snippet you provided has hooks that are micro scale, they want very specific,
   single bits of data, you cannot hook your loop content into these filters.
 * You need to find a more appropriate filter to hook. If the plugin code came from
   where I think it did, the filter ‘bawmrp_more_content’ may be the appropriate
   hook. Content returned to this filter will be output right after each plugin 
   link. Let’s assume you were able to create a function called ‘my_property_data()’
   that returns the needed content as a string instead of directly outputting it
   to the browser. To hook the filter with your function, you just need the line`
   add_filter('bawmrp_more_content', 'my_property_data');`
 *  Thread Starter [aronjeney](https://wordpress.org/support/users/aronjeney/)
 * (@aronjeney)
 * [13 years, 1 month ago](https://wordpress.org/support/topic/adding-custom-loop-to-plugin/#post-3638550)
 * Hi again bcworkz (your hitting all my threads :). Thanks for this input. I had
   concluded that what you are explaining is actually how I need to do it, however
   I am still in question as to how I would create a function for my code above (
   on the macro level). I am working on this at this very moment, just very slow
   moving. If you could provide some insight as to how I would create a function
   from my code above I would be even more grateful! Thanks for all your insight
   so far.
 *  Moderator [bcworkz](https://wordpress.org/support/users/bcworkz/)
 * (@bcworkz)
 * [13 years, 1 month ago](https://wordpress.org/support/topic/adding-custom-loop-to-plugin/#post-3638601)
 * How you would change template code into a hook function will depend on the nature
   of the hook. With action hooks, it is often possible to simply wrap the code 
   in a function definition so that the HTML is directly output when the action 
   fires. This does not always work so easily with some actions, and rarely so with
   filters.
 * Some actions and most filters expect you to return a value, not directly output
   HTML. The first step still is to wrap the template code in a function definition.
   The only other step, albeit a large one, is to collect all the HTML output into
   a string variable that will be returned to the apply_filters() call. A trivial
   example if your template code only consisted of the first three lines.
 *     ```
       function my_property_data($content) {
          $content .= '<div class="home-property-item">';
          $content .= '<div class="property-detail-block">';
          $content .= '<div class="property-pic-wrapper">';
          return $content;
       }
       ```
   
 * Note the apply_filters() call passed a $content parameter to which I simply appended
   more HTML, then returned the modified parameter. You need to examine the source
   code of any hook to determine what is passed to your hook function and what is
   done with the return value, the specifics will vary and you must match expectations.
 * Also note that with HTML output, you must be careful the quote types are well
   coordinated and escaped where applicable, or else you will have a huge mess. 
   That was a trivial example because the template code was all HTML, no PHP was
   involved. Another trivial transformation will occur when the template code is
   all PHP that does not generate any output. You simply remove the PHP block delimiters`
   <?php ?>`. This means you need to be familiar with WP template tags that do generate
   output. Watch out for these, as well as any `echo` and similar statements which
   also generate output. These must be converted to append content to $content instead
   of outputting it. In the case of `echo 'some text to output';` just replace with`
   $content .= 'some text to output';`
 * With template tags like the_permalink() that output HTML, there is invariably
   a variant that returns a value instead of outputting content, usually get_something()
   replaces the_something(). `the_permalink();` could be transformed to `$content.
   = get_permalink();`
 * Perhaps the trickiest transformation is for lines of mixed HTML and PHP content.
   `
   <a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>">` is transformed
   to `$output .= '<a href="' . get_permalink() . '" title="' . get_the_title() .'"
   >';` Be careful with quotes! Another example of mixed content: `<p class="<?php
   echo $property_status; ?>">` is transformed to `$output .= "<p class=\"$property_status\"
   >";` This time I used double quotes in PHP so I can have PHP expand $property_status
   for me instead of concatenating it. This means I need to escape HTML double quotes.
   This also would work, but is harder to read IMO (too many quotes to coordinate):`
   $output .= '<p class="' . $property_status .'">';` Finally, since HTML accepts
   either quote type, you could also do this: `$output .= "<p class='$property_status'
   >";` Also remember to use curly brackets {} around complex or ambiguous variables
   to be expanded inside double quoted strings. Example with a complex variable:`
   $output .= "<p class=\"{$property_status[0]->previous}\">";`
 * The main thing is to be careful and meticulous doing such a transformation, and
   be sure you understand what every PHP function is doing, as how it is handled
   varies accordingly. Good luck!
 *  Thread Starter [aronjeney](https://wordpress.org/support/users/aronjeney/)
 * (@aronjeney)
 * [13 years, 1 month ago](https://wordpress.org/support/topic/adding-custom-loop-to-plugin/#post-3638617)
 * Hey bcworkz, I really appreciate you taking the time to write all of this information.
   It really helps me understand the complexities of writing php on a micro scale
   vs macro scale as you worded it. You have definitely guided me in the right direction,
   however I have a lot of work to do to incorporate my php code from my template
   file into my function. I will continue to research more about this matter while
   using your input as reference. Again, thanks so much for your time. I will let
   you know how it turns out!
 *  Thread Starter [aronjeney](https://wordpress.org/support/users/aronjeney/)
 * (@aronjeney)
 * [13 years, 1 month ago](https://wordpress.org/support/topic/adding-custom-loop-to-plugin/#post-3638675)
 * Well, I am still having troubles adding and applying my own filters, however 
   I have been able to kindof hack the plugin code to call the html of my loop –
   not rocket science I know but I feel like I’m getting somewhere at least. That
   said, I’m really having trouble condensing my php properly either with filters
   or as it is now (still somewhat confused as what I need to do there).
 * See my current code below.
 *     ```
       $_content = apply_filters( 'bawmrp_more_content', $_content, $output );
       					$thumb_size = apply_filters( 'bawmrp_thumb_size', array( 300, 300 ) );
       					$thumb = has_post_thumbnail( $id ) ? get_the_post_thumbnail( $id, $thumb_size ) : '<img src="' . $no_thumb . '" height="' . $thumb_size[0] . '" width="' . $thumb_size[1] . '" />';
   
       					$list[] = '<div class="home-property-item">
       									<div class="property-detail-block">
       										<div class="property-pic-wrapper">
       											<a href="' . esc_url( apply_filters( 'the_permalink', get_permalink( $id ) ) ) . '">' . $thumb  . '</a>
       											<h4><a href="' . esc_url( apply_filters( 'the_permalink', get_permalink( $id ) ) ) . '">' . apply_filters( 'the_title', get_the_title( $id ) )  . '</a></h4>
       										</div>
   
       									   <div class="features-wrapper">
       									   		<span class="bed"><div class="value"></div></span>
       									   		<span class="bath"><div class="value"></div></span>
       									   		<span class="size"><div class="value"></div></span>
       									   		<div class="price-box">
       							                    <h5 class="price"></h5>
       							                </div>
       							            </div>
   
       								   		<div class="learnmore">
       											<a href="' . esc_url( apply_filters( 'the_permalink', get_permalink( $id ) ) ) . '" class="blue">LEARN MORE</a>
       										</div>
       							   		</div>
       							   </div>';
       ```
   
 * Again, I have wrapped the current thumbnail and title filters with my html. How
   would I go about condensing the following code to fit within the “bed” span class?
 * `<span class="bed"><div class="value"><?php echo get_post_meta($post->ID, 'locality_property_bedrooms',
   true); ?></div> <?php _e('Beds') ?></span>`
 * Again, really appreciate all the help. I really am trying to do this on my own
   but just not getting too far. Thanks again in advance!
 *  Thread Starter [aronjeney](https://wordpress.org/support/users/aronjeney/)
 * (@aronjeney)
 * [13 years, 1 month ago](https://wordpress.org/support/topic/adding-custom-loop-to-plugin/#post-3638678)
 * Ok, I have been able to call the post meta by adding _apply\_filters(‘get\_post\
   _meta’…_, HOWEVER, it is calling the post meta of the current post that is being
   viewed rather than the post meta of the manually added posts.
 * See my code below..
 * `<span class=”bed”><div class=”value”>’ . apply_filters( ‘get_post_meta’, get_post_meta(
   $post->ID, ‘locality_property_bedrooms’, true) ) . ‘</div>Beds</span>’
 * What am I doing wrong? :/
 *  Moderator [bcworkz](https://wordpress.org/support/users/bcworkz/)
 * (@bcworkz)
 * [13 years, 1 month ago](https://wordpress.org/support/topic/adding-custom-loop-to-plugin/#post-3638699)
 * Sorry to hear you are struggling with this. I know how frustrating it is. Believe
   it or not, your efforts will pay off later if you continue with any kind of coding.
   It’s all a learning experience. Perhaps not the most efficient way to learn. 
   When I learn this way, I tend to never forget what I learned though.
 * You appear to be confused with how filters work. For one thing, there is no ‘
   get_post_meta’ filter AFAIK. Either way, there’s little point in creating your
   own filters (what you do with apply_filters()) unless you anticipate others extending
   your code and you wish to provide a clean way for them to latch into particular
   processes to modify the results. The huge number of hooks in WP is what makes
   it easily extendable, once you understand how it all works. Instead of apply_filters(),
   you could simply directly assign whatever you pass as the 2nd parameter of apply_filters().
 * Of course, to hack WP, you use filters a lot, but never apply_filters(). You 
   hook into the apply_filters() calls that WP uses with add_filter(). The function
   that you specify in add_filter() ends up being called (via call_user_func()) 
   when the apply_filters() function is encountered in the WP core code. What value
   your filter function returns ends up being returned by the apply_filters() call.
 * In other words, apply_filters() does not alter anything, it creates the opportunity
   for others to alter something. In order to alter something that uses apply_filters(),
   you must hook into it with add_filter(). Review [Plugin_API#Filters](http://codex.wordpress.org/Plugin_API#Filters)
   for more detailed information. It’s specific for plugins, but the concept applies
   to themes and child themes as well.
 * Maybe an example will make more sense. Let’s say we want to wrap the output of
   all permalinks in a <span> block for special styling from our CSS page. We could
   do this without filters of course, but there are many cases where hooking the
   filter is the only viable option. In addition, the filter I hook is not the best
   one to use, but it more clearly illustrates the process. Even though my example
   is unrealistic, it should illustrate the concept.
 * Let’s say we have the following code on one of our templates somewhere:
    `echo
   get_permalink($post->ID);`
 * If we check the source code of get_permalink(), we find the final line is:
    `
   return apply_filters('post_link', $permalink, $post, $leavename);`
 * So now we know whatever is returned by apply_filters() is in turn returned by
   get_permalink(). And on our template, whatever is returned by get_permalink()
   is immediately echoed out to the user’s browser. Now we know if we hook ‘post_link’,
   what ever our filter function returns will be immediately echoed out to the browser.
   We can also see our filter function will be passed 3 different variables with
   useful data. As a rule, if we do nothing else, we should return the 2nd parameter
   $permalink to maintain the integrity of the filter stack. Remember that other
   plugins may be hooking the same filter. If we do not return anything, the chain
   is broken.
 * To hook the ‘post_link’ filter, we write:
    `add_filter('post_link', 'span_wrap_link',
   10, 3);`
 * ‘span_wrap_link’ is a function we will define next. 10 is the priority of execution
   in the filter stack. 10 is the default value. Smaller priority numbers (i.e. 
   1) get executed first, larger numbers (i.e. 99) last. There is usually an advantage
   to being last so your function has final say on the outcome. 3 is the number 
   of parameters passed to our filter function. If you only need the 2nd ($permalink)
   parameter and the default priority is fine, you can omit the last 2 parameters.
   Such is the case here, but we’ll accept all 3 parameters because we can. You 
   could for example, check a field in the $post parameter (the $post object the
   link points to) and only apply the <span> block if the field is a certain value,
   say if the post is by a certain author.
 * To simply wrap all links in a <span> block, we write:
 *     ```
       function span_wrap_link($permalink, $post, $leavename) {
          return "<span class="permalink">$permalink</span>";
       }
       ```
   
 * Now, PHP inserts the value of $permalink into our <span> block string (because
   the variable reference is inside a double quoted string), which is returned to
   the apply_filters() function, apply_filters() in turn returns our modified link
   to get_permalink(), which in turn returns the link to our echo statement which
   results in the link being echoed out to the user.
 * A very long way of saying get rid of the apply_filters(‘get_post_meta’) bit and
   just call get_post_meta() directly. As far as the meta coming from the current
   post instead of the manually added, this is coming from the $post->ID parameter.
   $post in WP loops is the current post object. You need to supply the ID of your
   manually added post to get the correct meta.
 * Look forward to the HUGE sense of accomplishment you will get once you finally
   get this working 🙂
 *  Thread Starter [aronjeney](https://wordpress.org/support/users/aronjeney/)
 * (@aronjeney)
 * [13 years, 1 month ago](https://wordpress.org/support/topic/adding-custom-loop-to-plugin/#post-3638734)
 * I really appreciate the time that you put into writing this post and your interest
   in helping me and others learn. Although I was able to accomplish what I needed
   by “hacking” the current filter, I really value this lesson and your willingness
   to help others. Thanks so much again for all your help so far. I’ve seen you 
   around the support forum quite a bit so Im sure this wont be the last time we
   chat. Thanks again bcworkz!

Viewing 8 replies - 1 through 8 (of 8 total)

The topic ‘Adding custom loop to plugin’ is closed to new replies.

## Tags

 * [apply_filter](https://wordpress.org/support/topic-tag/apply_filter/)
 * [custom loop](https://wordpress.org/support/topic-tag/custom-loop/)

 * In: [Hacks](https://wordpress.org/support/forum/plugins-and-hacks/hacks/)
 * 8 replies
 * 2 participants
 * Last reply from: [aronjeney](https://wordpress.org/support/users/aronjeney/)
 * Last activity: [13 years, 1 month ago](https://wordpress.org/support/topic/adding-custom-loop-to-plugin/#post-3638734)
 * Status: not resolved

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