diff -up libkolabxml-1.2.0/src/php/CMakeLists.txt.swig libkolabxml-1.2.0/src/php/CMakeLists.txt
--- libkolabxml-1.2.0/src/php/CMakeLists.txt.swig	2022-09-19 21:22:05.943413603 +0200
+++ libkolabxml-1.2.0/src/php/CMakeLists.txt	2022-09-19 21:22:54.036485986 +0200
@@ -66,7 +66,7 @@ if(NOT PHP_VERSION_ID VERSION_LESS ${PHP
 
   install( FILES
           ${CMAKE_CURRENT_BINARY_DIR}/kolabformat.php
-          DESTINATION ${PHP_INSTALL_DIR}
+          DESTINATION ${PHP_INSTALL_DIR} OPTIONAL
       )
 
 else()