Remove the option to add an additional PHP version on the slave of a mirrored cluster (see #4197).

interface/web/admin/form/server_php.tform.php

@@ -89,7 +89,7 @@ $form["tabs"]['php_name'] = array (
 			'formtype' => 'SELECT',
 			'default' => '',
 			'datasource' => array (  'type' => 'SQL',
-				'querystring' => 'SELECT server_id,server_name FROM server WHERE {AUTHSQL} ORDER BY server_name',
+				'querystring' => 'SELECT server_id,server_name FROM server WHERE mirror_server_id = 0 AND {AUTHSQL} ORDER BY server_name',
 				'keyfield'=> 'server_id',
 				'valuefield'=> 'server_name'
 			),