Add option to override where to install mod_php.so Apache module

The mod_php.so is by default installed to Apache's module directory on
the host system and this might interfere with some possible edge cases
where some other install prefix is used. For example, during development
of the build system itself.

Author: petk

cmake/ext/skeleton/CMakeLists.txt.in

@@ -121,7 +121,7 @@ install(
     COMPONENT php-development
 )
 
-set(PHP_EXTENSION_%EXTNAMECAPS% TRUE)
+set(PHP_EXT_%EXTNAMECAPS%_ENABLED TRUE)
 
 # Create configuration header.
 configure_file(cmake/config.h.in config.h)

cmake/ext/skeleton/cmake/config.h.in.in

@@ -1,2 +1,2 @@
 /* Define to 1 if the PHP extension '%EXTNAME%' is available. */
-#cmakedefine PHP_EXTENSION_%EXTNAMECAPS% 1
+#cmakedefine PHP_EXT_%EXTNAMECAPS%_ENABLED 1

cmake/sapi/apache2handler/CMakeLists.txt

@@ -3,13 +3,25 @@
 
 Configure the `apache2handler` PHP SAPI.
 
-## PHP_SAPI_APACHE2HANDLER
+## Configuration options
+
+### PHP_SAPI_APACHE2HANDLER
 
 * Default: `OFF`
 * Values: `ON|OFF`
 
 Enable the shared Apache 2 handler SAPI module.
 
+## PHP_SAPI_APACHE2HANDLER_INSTALL_DIR
+
+* Default: The path to the Apache modules directory of the host system
+  (`Apache_LIBEXEC`).
+
+The path where to install the PHP Apache module (`mod_php.so`). Relative path is
+interpreted as being relative to the installation prefix `CMAKE_INSTALL_PREFIX`.
+
+## About
+
 Loadable via Apache's Dynamic Shared Object (DSO) support. If Apache will use
 PHP together with one of the threaded Multi-Processing Modules (MPMs), PHP must
 be configured and built with `PHP_THREAD_SAFETY` set to `ON`. Thread safety will
@@ -21,11 +33,24 @@ with the `APACHE_ROOT` and `Apache_APXS_EXECUTABLE` variables.
 
 For example:
 
-```cmake
+```sh
 cmake -B php-build -DPHP_SAPI_APACHE2HANDLER=ON -DAPACHE_ROOT=/opt/apache2
 # or
 cmake -B php-build -DPHP_SAPI_APACHE2HANDLER=ON -DApache_EXECUTABLE=/opt/apache2/bin/apxs
 ```
+
+The path, where to install the PHP Apache module, can be overridden with the
+`PHP_SAPI_APACHE2HANDLER_INSTALL_DIR` variable. This might be used in edge cases
+where some specific custom installation prefix is used to avoid insuficcient
+permissions of the default location on the host, or when developing the PHP
+build system.
+
+```sh
+cmake \
+  -B <build-dir> \
+  -DPHP_SAPI_APACHE2HANDLER=ON \
+  -DPHP_SAPI_APACHE2HANDLER_INSTALL_DIR=/custom/path/to/lib/apache2/modules
+```
 #]=============================================================================]
 
 include(FeatureSummary)
@@ -38,6 +63,15 @@ add_feature_info(
   "Apache HTTP server module"
 )
 
+set(
+  CACHE{PHP_SAPI_APACHE2HANDLER_INSTALL_DIR}
+  TYPE STRING
+  HELP "The path to the Apache modules directory to install PHP Apache module"
+  VALUE ""
+)
+set_property(CACHE PHP_SAPI_APACHE2HANDLER_INSTALL_DIR PROPERTY TYPE PATH)
+mark_as_advanced(PHP_SAPI_APACHE2HANDLER_INSTALL_DIR)
+
 if(NOT PHP_SAPI_APACHE2HANDLER)
   return()
 endif()
@@ -75,6 +109,13 @@ set_package_properties(
     PURPOSE "Necessary to enable the Apache PHP SAPI."
 )
 
+if(Apache_FOUND AND NOT PHP_SAPI_APACHE2HANDLER_INSTALL_DIR)
+  set_property(
+    CACHE PHP_SAPI_APACHE2HANDLER_INSTALL_DIR
+    PROPERTY VALUE "${Apache_LIBEXECDIR}"
+  )
+endif()
+
 target_link_libraries(
   php_sapi_apache2handler
   PRIVATE
@@ -146,9 +187,9 @@ endif()
 install(
   TARGETS php_sapi_apache2handler
   LIBRARY
-    DESTINATION ${Apache_LIBEXECDIR}
+    DESTINATION ${PHP_SAPI_APACHE2HANDLER_INSTALL_DIR}
     COMPONENT php-sapi-apache2handler
   RUNTIME
-    DESTINATION ${Apache_LIBEXECDIR}
+    DESTINATION ${PHP_SAPI_APACHE2HANDLER_INSTALL_DIR}
     COMPONENT php-sapi-apache2handler
 )