Enable Custom Field Searching With Wordpress 2.6 | Talk In Code

I have previously talked about enable custom field search in Wordpress, but that involved altering the main Wordpress files, which is a big no-no.

So is there an alternative? Well, yes, otherwise I wouldn’t have bothered writing the post!

To enable custom field (also called Wordpress metadata) searching you need to set up two things.

First you need to have created a custom field (or two) and added this to a number of posts.

Next, you need to have a custom search form that has the name of thefield set as the name of an input box. You don’t even need the normal sinput box that Wordpress uses as default.

Open up your template functions.php file and add in the following three lines of code.

add_filter('posts_join','search_metadata_join');
add_filter('posts_where','search_metadata');
add_filter('posts_groupby','search_meta_groupby');

This adds three callback filters to Wordpress at run time. Theposts_join will add the meta table into our query so that we can workwith it. The posts_where will be the main function where all of ourwhere clauses will be build. Finally, posts_groupby will stop multipleposts appearing for the same term. All we have to do now is include thequeries we need in order to enable custom field searching. I will doeach of the callback functions in the order they appeared above.

function search_metadata_join($join) {
 global $wp_query, $wpdb, $wp_version;
  // add in check for older versions
 if($wp_version >= '2.3'){
  $join .= " LEFT JOIN $wpdb->postmeta AS m ON ($wpdb->posts.ID = m.post_id) ";
 }else{
  $join .= "LEFT JOIN $wpdb->postmeta ON $wpdb->posts.ID = $wpdb->postmeta.post_id ";
 }
 
 return $join;
}

The search_metadata() function has a array variable called$metaVars. This contains an array of the names of the custom fieldsthat you want to search through. Each item in the array is checked tosee if it has a value, and if it does it is included in a string calledclause. The function is set up to allow for any of the custom fieldsbeing true, which is what I wanted it do to.

function search_metadata($where) {
 global $wp_query, $wpdb, $wp_version;
 
 $metaVars = array('custom1','custom2');
 $where .= ' AND (';
 foreach($metaVars as $metaValue=>$metaKey){
  if(!empty($_GET[$metaKey])){
   if($wp_version >= '2.3'){
    $clause .= " OR (m.meta_key = '".$metaKey."' AND m.meta_value LIKE '%".$wpdb->escape($_GET[$metaKey]) . "%') ";
   }else{
    $clause .= " OR (meta_key = '".$metaKey."' AND meta_value LIKE '%" . $wpdb->escape($_GET[$metaKey]) . "%') ";
   }
  }
 }
 $where .= substr($clause,3).') ';
 return $where;
}

Finally, here is the search_meta_groupby() function. I pulled this from the wordpress.org site and adapted it slightly.

function search_meta_groupby( $groupby ){
 global $wpdb;
 
 // we need to group on post ID
 $mygroupby = "{$wpdb->posts}.ID";
 if( preg_match( "/$mygroupby/", $groupby )) {
  // grouping we need is already there
  return $groupby;
 }
 
 if( !strlen(trim($groupby))) {
  // groupby was empty, use ours
  return $mygroupby;
 }
 
 // wasn't empty, append ours
 return $groupby . ", " . $mygroupby;
}

All this is designed to get you started in creating custom fieldWordpress searching. You might have to tweak the code involved herebefore you get it working.