diff --git a/tools/run_tests/run_interop_tests.py b/tools/run_tests/run_interop_tests.py
index c9e2f09b2d2..40e1b6e0cc6 100755
--- a/tools/run_tests/run_interop_tests.py
+++ b/tools/run_tests/run_interop_tests.py
@@ -230,7 +230,10 @@ class PHPLanguage:
     return _SSL_CERT_ENV
 
   def global_env(self):
-    return {}
+    # need to manually copy to each jenkins machine if we run into github
+    # rate limit when running `composer install`
+    return {"BUILD_INTEROP_DOCKER_EXTRA_ARGS":
+            "-v /var/local/.composer/auth.json:/root/.composer/auth.json:ro"}
 
   def __str__(self):
     return 'php'