dont install mapscript.php with newer swig
cf https://github.com/MapServer/MapServer/commit/a3d65f412e58bd7611830db49c92e2e6fb67caf3

Index: mapscript/phpng/CMakeLists.txt
--- mapscript/phpng/CMakeLists.txt.orig
+++ mapscript/phpng/CMakeLists.txt
@@ -84,8 +84,4 @@ set_target_properties(${SWIG_MODULE_mapscript_REAL_NAM
 
 if(NOT WIN32)
   install(TARGETS php_mapscriptng DESTINATION ${PHP_EXTENSION_DIR})
-  # check if we must install the required file containing MapServer constants and functions
-  if(${SWIG_VERSION} LESS_EQUAL 4.0.2)
-     install(FILES ${CMAKE_CURRENT_BINARY_DIR}/mapscript.php DESTINATION ${PHP_EXTENSION_DIR} COMPONENT dev)
-  endif()
 endif()
