Check for php program in autoconf

Use the detected PHP (minimum 7.1) to run gen_stubs, and other
code generation scripts in the future.

Author: nikic

build/Makefile.global

@@ -142,17 +142,11 @@ prof-clean:
 prof-use:
 	CCACHE_DISABLE=1 $(MAKE) PROF_FLAGS=-fprofile-use all
 
-# only php above 7.1.0 supports nullable return type
 %_arginfo.h: %.stub.php
 	@if test -e "$(top_srcdir)/build/gen_stub.php"; then \
-		if test ! -z "$(PHP_EXECUTABLE)" && test -x "$(PHP_EXECUTABLE)"; then \
+		if test ! -z "$(PHP)" && test -x "$(PHP)"; then \
 			echo Parse $< to generate $@;\
-			$(PHP_EXECUTABLE) $(top_srcdir)/build/gen_stub.php $<; \
-		elif type php >/dev/null 2>/dev/null; then \
-			if test `php -v | head -n1 | cut -d" " -f 2 | sed "s/$$/\n7.0.99/" | sort -rV | head -n1` != "7.0.99"; then \
-				echo Parse $< to generate $@;\
-				php $(top_srcdir)/build/gen_stub.php $<; \
-			fi; \
+			$(PHP) $(top_srcdir)/build/gen_stub.php $<; \
 		fi; \
 	fi;
 

build/php.m4

@@ -1876,6 +1876,30 @@ AC_DEFUN([PHP_PROG_RE2C],[
   PHP_SUBST(RE2C)
 ])
 
+AC_DEFUN([PHP_PROG_PHP],[
+  AC_CHECK_PROG(PHP, php, php)
+
+  if test -n "$PHP"; then
+    AC_MSG_CHECKING([for php version])
+    php_version=$($PHP -v | head -n1 | cut -d ' ' -f 2)
+    if test -z "$php_version"; then
+      php_version=0.0.0
+    fi
+    ac_IFS=$IFS; IFS="."
+    set $php_version
+    IFS=$ac_IFS
+    php_version_num=`expr [$]{1:-0} \* 10000 + [$]{2:-0} \* 100 + [$]{3:-0}`
+    dnl Minimum supported version for gen_stubs.php is PHP 7.1.
+    if test "$php_version_num" -lt 70100; then
+      AC_MSG_RESULT([$php_version (too old)])
+      unset PHP
+    else
+      AC_MSG_RESULT([$php_version (ok)])
+    fi
+  fi
+  PHP_SUBST(PHP)
+])
+
 dnl ----------------------------------------------------------------------------
 dnl Common setup macros: PHP_SETUP_<what>
 dnl ----------------------------------------------------------------------------

configure.ac

@@ -155,6 +155,7 @@ dnl Checks for some support/generator progs.
 PHP_PROG_AWK
 PHP_PROG_BISON([3.0.0])
 PHP_PROG_RE2C([0.13.4])
+PHP_PROG_PHP()
 
 PHP_ARG_ENABLE([re2c-cgoto],
   [whether to enable computed goto gcc extension with re2c],