diff -up ./config.m4.old ./config.m4
--- ./config.m4.old	2024-10-21 08:45:48.099506102 +0200
+++ ./config.m4	2024-10-21 08:46:42.647663062 +0200
@@ -26,5 +26,6 @@ if test "$PHP_AWSCRT" != "no"; then
     # Sources for the PHP extension itself
     AWSCRT_SOURCES=ext/awscrt.c
     PHP_NEW_EXTENSION(awscrt, $AWSCRT_SOURCES, $ext_shared)
+    PHP_ADD_BUILD_DIR($ext_builddir/ext)
     PHP_ADD_MAKEFILE_FRAGMENT
 fi
diff -up ./Makefile.frag.old ./Makefile.frag
--- ./Makefile.frag.old	2024-10-21 08:45:58.170904348 +0200
+++ ./Makefile.frag	2024-10-21 09:29:21.845818243 +0200
@@ -1,7 +1,7 @@
 
 INT_DIR=$(builddir)/build/install
 CMAKE_BUILD_DIR=$(builddir)/cmake_build
-GENERATE_STUBS=$(shell expr `php --version | head -1 | cut -f 2 -d' '` \>= 7.1)
+GENERATE_STUBS=$(shell expr `$(PHP_EXECUTABLE) --version | head -1 | cut -f 2 -d' '` \>= 7.1)
 
 CMAKE = cmake3
 ifeq (, $(shell which cmake3))
@@ -58,17 +58,18 @@ extension: $(builddir)/ext/awscrt.lo
 # Force the crt object target to depend on the CRT static library
 $(builddir)/ext/awscrt.lo: $(builddir)/ext/awscrt.c
 
-$(builddir)/ext/awscrt.c: $(CMAKE_BUILD_DIR)/aws-crt-ffi-static/libaws-crt-ffi.a $(builddir)/ext/api.h $(builddir)/ext/awscrt_arginfo.h
+$(builddir)/ext/awscrt.c: $(CMAKE_BUILD_DIR)/aws-crt-ffi-static/libaws-crt-ffi.a $(srcdir)/ext/api.h $(srcdir)/ext/awscrt_arginfo.h
 
-$(builddir)/ext/awscrt_arginfo.h: $(srcdir)/ext/awscrt.stub.php $(srcdir)/gen_stub.php
+$(srcdir)/ext/awscrt_arginfo.h: $(srcdir)/ext/awscrt.stub.php $(srcdir)/gen_stub.php
 ifeq ($(GENERATE_STUBS),1)
 	# generate awscrt_arginfo.h
-	mkdir -p $(builddir)/ext && php $(srcdir)/gen_stub.php --minimal-arginfo $(srcdir)/ext/awscrt.stub.php
+	$(PHP_EXECUTABLE) $(srcdir)/gen_stub.php --minimal-arginfo $(srcdir)/ext/awscrt.stub.php
 endif
 
 # transform/install api.h from FFI lib
 $(srcdir)/ext/api.h: $(srcdir)/crt/aws-crt-ffi/src/api.h
-	php $(srcdir)/gen_api.php $(srcdir)/crt/aws-crt-ffi/src/api.h > $(srcdir)/ext/api.h
+	# generate api.h
+	$(PHP_EXECUTABLE) $(srcdir)/gen_api.php $(srcdir)/crt/aws-crt-ffi/src/api.h > $(srcdir)/ext/api.h
 
 # install api.h to ext/ as well
 $(builddir)/ext/api.h : $(srcdir)/ext/api.h