diff --git a/build/php.m4 b/build/php.m4
index 77a99783e2edb..662feb8c58ffd 100644
--- a/build/php.m4
+++ b/build/php.m4
@@ -1319,24 +1319,20 @@ int main(void)
 dnl
 dnl PHP_FOPENCOOKIE
 dnl
-AC_DEFUN([PHP_FOPENCOOKIE], [
-  AC_CHECK_FUNC(fopencookie, [have_glibc_fopencookie=yes])
-
-  if test "$have_glibc_fopencookie" = "yes"; then
-dnl glibcs (since 2.1.2?) have a type called cookie_io_functions_t.
-AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
-#ifndef _GNU_SOURCE
-#define _GNU_SOURCE
-#endif
-#include <stdio.h>
-]], [[cookie_io_functions_t cookie;]])],[have_cookie_io_functions_t=yes],[])
-
-    if test "$have_cookie_io_functions_t" = "yes"; then
-dnl Newer glibcs have a different seeker definition.
-AC_RUN_IFELSE([AC_LANG_SOURCE([[
-#ifndef _GNU_SOURCE
-#define _GNU_SOURCE
-#endif
+dnl Check for cookie_io_functions_t type and fopencookie(). When using glibc,
+dnl checks here require _GNU_SOURCE defined via AC_USE_SYSTEM_EXTENSIONS. Some
+dnl glibc versions started using the off64_t in fopencookie seeker definition,
+dnl which is in transition to use the POSIX standard off_t on 32-bit (with large
+dnl file support enabled) and 64-bit.
+dnl
+AC_DEFUN([PHP_FOPENCOOKIE],
+[AC_CHECK_TYPE([cookie_io_functions_t], [AC_CHECK_FUNCS([fopencookie])],,
+  [#include <stdio.h>])
+dnl Check if glibc might use off64_t seeker definition.
+AS_VAR_IF([ac_cv_func_fopencookie], [yes],
+  [AC_CACHE_CHECK([whether fopencookie seeker uses off64_t],
+    [php_cv_type_cookie_off64_t],
+    [AC_RUN_IFELSE([AC_LANG_SOURCE([
 #include <stdio.h>
 #include <stdlib.h>
 
@@ -1345,48 +1341,35 @@ struct cookiedata {
 };
 
 ssize_t reader(void *cookie, char *buffer, size_t size)
-{ return size; }
+{ (void)cookie; (void)buffer; return size; }
 ssize_t writer(void *cookie, const char *buffer, size_t size)
-{ return size; }
+{ (void)cookie; (void)buffer; return size; }
 int closer(void *cookie)
-{ return 0; }
+{ (void)cookie; return 0; }
 int seeker(void *cookie, off64_t *position, int whence)
-{ ((struct cookiedata*)cookie)->pos = *position; return 0; }
+{ ((struct cookiedata*)cookie)->pos = *position; (void)whence; return 0; }
 
 cookie_io_functions_t funcs = {reader, writer, seeker, closer};
 
 int main(void) {
   struct cookiedata g = { 0 };
   FILE *fp = fopencookie(&g, "r", funcs);
-
-  if (fp && fseek(fp, 8192, SEEK_SET) == 0 && g.pos == 8192)
+  if (fp && fseek(fp, 8192, SEEK_SET) == 0 && g.pos == 8192) {
     return 0;
+  }
   return 1;
 }
-
-]])], [
-  cookie_io_functions_use_off64_t=yes
-], [
-  cookie_io_functions_use_off64_t=no
-], [
-  dnl Cross compilation.
-  case $host_alias in
-    *linux*)
-      cookie_io_functions_use_off64_t=yes
-      ;;
-    *)
-      cookie_io_functions_use_off64_t=no
-      ;;
-  esac
+])],
+  [php_cv_type_cookie_off64_t=yes],
+  [php_cv_type_cookie_off64_t=no],
+  [AS_CASE([$host_alias],
+    [*linux*], [php_cv_type_cookie_off64_t=yes],
+    [php_cv_type_cookie_off64_t=no])]
+  )])
+  AS_VAR_IF([php_cv_type_cookie_off64_t], [yes],
+    [AC_DEFINE([COOKIE_SEEKER_USES_OFF64_T], [1],
+      [Whether fopencookie seeker uses off64_t.])])
 ])
-
-      AC_DEFINE(HAVE_FOPENCOOKIE, 1, [ ])
-
-      if test "$cookie_io_functions_use_off64_t" = "yes" ; then
-        AC_DEFINE(COOKIE_SEEKER_USES_OFF64_T, 1, [ ])
-      fi
-    fi
-  fi
 ])
 
 dnl ----------------------------------------------------------------------------