$activityTypes = CRM_Core_PseudoConstant::activityType();
$activity = CRM_Activity_BAO_Activity::create([ 'activity_type_id' => array_search('Meeting', CRM_Core_PseudoConstant::activityType(TRUE)), // Other required activity fields ]);
$emailActivities = civicrm_api3('Activity', 'get', [ 'activity_type_id' => array_search('Email', CRM_Core_PseudoConstant::activityType(TRUE)), // Other optional filtering parameters ]);Overall, the CRM_Core_PseudoConstant activityType library provides a convenient and consistent way of working with activity types within CiviCRM.