Adds a new 'Doors open' field to the event editor. For a more information see: http://www.slimndap.com/a-new-event-editor/.

wp-theatre-add-doors-open-field.php

/**
 * Adds a 'Doors open' field to the event editor.
 * 
 * Prepends the new field by filtering the current fields of the event editor
 * using the 'wpt/event_editor/fields' hook.
 * 
 * @param 	array 	$fields		The current fields of the event editor.
 * @param 	int 	$event_id	The ID of the event being edited.
 * @return 	array				The new fields of the event editor.
 */
function add_doors_open_field($fields, $event_id) {
  array_unshift( $fields, array( 'id' => 'doors_open', 'title' => 'Doors open' ) );
  return $fields;
}
add_filter( 'wpt/event_editor/fields', 'add_doors_open_field', 10, 2 );