Simplify php vernum detection

Author: pinepain

config.m4

@@ -9,7 +9,7 @@ if test "$PHP_REF" != "no"; then
 
   AC_MSG_CHECKING([Check for supported PHP versions])
   PHP_REF_FOUND_VERSION=`${PHP_CONFIG} --version`
-  PHP_REF_FOUND_VERNUM=`echo "${PHP_REF_FOUND_VERSION}" | $AWK 'BEGIN { FS = "."; } { printf "%d", ([$]1 * 100 + [$]2) * 100 + [$]3;}'`
+  PHP_REF_FOUND_VERNUM=`${PHP_CONFIG} --vernum`
 
   if test "$PHP_REF_FOUND_VERNUM" -lt "70003"; then
     AC_MSG_ERROR([not supported. Need a PHP version >= 7.0.3 (found $PHP_REF_FOUND_VERSION)])