diff --git a/UPGRADING.INTERNALS b/UPGRADING.INTERNALS
index c3b49d9d888fc..79e2b3d3789ec 100644
--- a/UPGRADING.INTERNALS
+++ b/UPGRADING.INTERNALS
@@ -221,6 +221,8 @@ PHP 8.4 INTERNALS UPGRADE NOTES
        - ac_cv_write_stdout                -> php_cv_have_write_stdout
      and all other checks wrapped with their belonging cache variables (see *.m4
      source files for details).
+   - New configure-phase environment variable PHP_EXTRA_CFLAGS to append
+     additional build-time CFLAGS to the PHP build.
 
  c. Windows build system changes
    - The configure options --with-oci8-11g, --with-oci8-12c, --with-oci8-19,
diff --git a/configure.ac b/configure.ac
index f30f58983fa3b..8e84fdae36b8e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1431,6 +1431,12 @@ AS_VAR_IF([PHP_BUILD_ARCH],,,
   [AC_DEFINE_UNQUOTED([PHP_BUILD_ARCH], ["$PHP_BUILD_ARCH"],
     [The build architecture.])])
 
+AC_ARG_VAR([PHP_EXTRA_CFLAGS],
+  [Additional build-phase compilation options appended to CFLAGS when building
+  PHP; these are isolated from the Autoconf configure checks and its CFLAGS])
+AS_VAR_IF([PHP_EXTRA_CFLAGS],,, [EXTRA_CFLAGS=$PHP_EXTRA_CFLAGS])
+
+PHP_SUBST([EXTRA_CFLAGS])
 PHP_SUBST([PHP_FASTCGI_OBJS])
 PHP_SUBST([PHP_SAPI_OBJS])
 PHP_SUBST([PHP_BINARY_OBJS])