Merge pull request #1518 from stanley-cheung/php_ignore_vendor_folder

ignore PHP vendor/ folder
diff --git a/src/php/.gitignore b/src/php/.gitignore
index 36c8721..ecde2ca 100644
--- a/src/php/.gitignore
+++ b/src/php/.gitignore
@@ -19,3 +19,4 @@
 
 ext/grpc/ltmain.sh
 composer.lock
+vendor/