If you are auditing a legacy system, these are the most relevant GitHub-hosted resources:
The script first sends a request with ?-s appended. If the response returns raw PHP code instead of executed HTML, the target is vulnerable. php 5416 exploit github
Whether the attacker uses a buffer overflow from line 5416 or a modern RCE, the defense strategy is the same. Do not rely on security by obscurity. If you are auditing a legacy system, these