apply_filters_ref_array( 'posts_where', string $where, WP_Query $query )

More Information

• This filter applies to the posts where clause and allows you to restrict which posts will show up in various areas of the site. Combined with restrict_manage_posts it allows you to only show posts matching specific conditions.

  Here is an example to match the restrict_manage_posts example:

  add_filter( 'posts_where' , 'posts_where' );
  
  function posts_where( $where ) {
  
  	if( is_admin() ) {
  		global $wpdb;
  		
  		if ( isset( $_GET['author_restrict_posts'] ) && !empty( $_GET['author_restrict_posts'] ) && intval( $_GET['author_restrict_posts'] ) != 0 ) {
  			$author = intval( $_GET['author_restrict_posts'] );
  		
  			$where .= " AND ID IN (SELECT object_id FROM {$wpdb->term_relationships} WHERE term_taxonomy_id=$author )";
  		}
  	}
  	return $where;
  }

  Depending on setup, if we had a custom post type of type ‘book’ with a taxonomy (category style) of type ‘author’, this filter would allow us to only show books written by a specific author.

• Certain functions which retrieve posts do not run filters, so the posts_where filter functions you attach will not modify the query. To overcome this, set suppress_filters to false in the argument array passed to the function. The following code sample illustrates this.

  	//some function that modifies the query
  	function useless_condition ( $where ) { return $where . ' AND 1=1 '; }
  
  	//attach your function to the posts_where filter
  	add_filter( 'posts_where' , 'useless_condition' );
  
  	//get posts AND make sure filters are NOT suppressed
  	$posts = get_posts( array( 'suppress_filters' => FALSE ) );