How to add an new Event Attribute Teacher to the events page and make it searchable.

I added the new attribute "Teacher" with allowed values "Abi" and "Lou" to the EM Events listing and single event pages. This bit is straight forward so not much detail required...

1. First add the new attribute and its allowed values with
   Events | Settings | General 
   Event Attributes : #_ATT{teacher}{Abi|Lou} 
   It can now be added to events.
    
2. Next add the attribute (and appropriate headings) to the templates in
   Settings | Formatting | Events.
   Both the default event list and Singel Event page templates were tweaked.
   It will now be displayed in Events.

Here's the meat. How to use this new attribute in the EM search form. Customise as you wish. I used the add themes functions.php method...

<?php
...
 // START EM Custm Attribute "Teacher" search
 /* Create a new search attribute form entry for our new Event Attribute "teacher" (#_ATT{teacher})
 The values are hard-coded but could probably be automatically selected
 Add this field to the search form using an EM action.
 nb. The action doc'd here http://wp-events-plugin.com/tutorials/adding-custom-event-search-form-fields/
 does not seem to exist so use the footer one for inclusion in advanced search or the header one
 for normal search. Read the source Luke.
 */
 function my_teacher_search_field(){ ?>
 <div class="em-search-teacher em-search-field">
 <label>Teacher</label>
 <select name="teacher">
 <option value=''>All Teachers</option>
 <option value="Abi" <?php echo ((array_key_exists('teacher', $_POST)) && $_POST['teacher'] == "Abi") ? 'selected="selected"':''; ?>>Abi</option>
 <option value="Lou" <?php echo ((array_key_exists('teacher', $_POST)) && $_POST['teacher'] == "Lou") ? 'selected="selected"':''; ?>>Lou</option>
 </select>
 </div>
 <?php }
 add_action('em_template_events_search_form_footer', 'my_teacher_search_field');
 //
 /* Hook the new search attribute teacher into default search filter,
 so it isn’t ignored when Events Manager creates an events search query
 */
 function my_teacher_search($searches, $array){
 if( !empty($array['teacher']) ){
 $searches['teacher'] = $array['teacher'];
 }
 return $searches;
 }
 add_filter('em_events_get_default_search','my_teacher_search',1,2);

 /* This isn't needed. It seems that inclusion in the default_search filter
 is all thats needed. See http://wp-events-plugin.com/tutorials/adding-custom-event-search-form-fields
 */
 //function my_teacher_accepted_searches($searches){
 // $searches[] = 'teacher';
 // return $searches;
 //}
 //add_filter('em_accepted_searches','my_teacher_accepted_searches',1,1);

 /* Can't hook into em_events_get filter as doc'd here
 http://wp-events-plugin.com/tutorials/creating-custom-event-search-attributes/
 as we need to join with kal_postmeta and not just filter kal_em_events
 so append a subquery via sql_conditions hook to find kal_postmeta using our new search attribute and return valid
 posts ids for main event query that is internally appended to display.
 */
 function my_teacher_conditions($conditions, $args){
 if( !empty($args['teacher'])) {
 $teacherval = $args['teacher'];
 $conditions['teacher'] = " (kal_em_events.post_id IN ( SELECT post_id FROM kal_postmeta WHERE (kal_postmeta.meta_key = 'teacher' AND kal_postmeta.meta_value = '$teacherval')))";
 }
 return $conditions;
 }
 add_filter( 'em_events_build_sql_conditions', 'my_teacher_conditions',1,2);
 //
 // END EM Custom Attribute Teacher Search
...
?>