Add Custom Event Attribute in your Event Search form

/*
 This snippet will add Custom Event Attribute in your Event Search form
 */

/*
   Step 1: add this custom filters in your theme functions.php or thru wp-content/mu-plugins/functions.php(create this php file or directory if this does not exists yet)

   NOTE: Change ContactName with your attribute name
 */

/************************************/

 function em_ContactName_get_default_search($searches, $array)
{
	if( !empty($array['ContactName'])){
		$searches['ContactName'] = $array['ContactName'];
	}
	return $searches;
}
add_filter('em_events_get_default_search','em_ContactName_get_default_search',1,2);

add_filter('em_events_get','em_em_ContactName_get_default_search_events_get',1,2);
function em_em_ContactName_get_default_search_events_get($events, $args)
{
	if( !empty($args['ContactName'])){

		$event_types = explode(',', $args['ContactName']);
		foreach($events as $event_key => $EM_Event){
			if( !in_array($EM_Event->event_attributes['ContactName'], $event_types) ){
				unset($events[$event_key]);
			}
		}
	}
	return $events;
}

function em_contactname_att($args){
 $args['ContactName'] = $_REQUEST['ContactName'];
 return $args;
}
add_filter('em_content_events_args','em_contactname_att',1,1);

/************************************/

/*
   Step 2: Create this php template and directory in your theme directory:

   wp-contents > Themes > Your Theme Name > (create this folder) plugins > (create this folder) events-manager > (create this folder) templates > (create this folder) search > (create this file) categories.php

   THEN edit this categories.php THEN copy the contents from wp-content/plugins/events-manager/templates/templates/search/categories.php and (add at the bottom) paste the following:
 */

 /************************************/
 <!-- START Custom Event Attributes -->
<?php
 //NOTE: Change ContactName with your attribute name
 //NOTE: you might need to modify this to prevent duplicate attribute being added to the options
?>
<?php
 $events = EM_Events::get($args);
?>
<div class="em-search-event-attributes em-search-field">
 <label>Event Attributes </label>
 <select name="ContactName">
  <option> </option>
  <?php foreach($events as $EM_Event){ ?>
    <?php if ( !empty($EM_Event->event_attributes['ContactName']) ): ?>
    <option value="<?php echo $EM_Event->event_attributes['ContactName']; ?>"> <?php echo $EM_Event->event_attributes['ContactName']; ?> </option>
    <?php endif; ?>
  <?php } ?>
 </select>
</div>
 /************************************/