use absolute function call

src/Client/RedmineClient.php

@@ -26,8 +26,8 @@ final class RedmineClient
             $item->expiresAfter(3600);
             $item->tag([$api, $method]);
 
-            $apiClient = $this->getClient()->getApi($api);
-            $value = call_user_method_array($method, $apiClient, $arguments);
+            $client = $this->getClient()->getApi($api);
+            $value = \call_user_method_array($method, $client, $arguments);
 
             return $value;
         });