This indicates an attack attempt to exploit an Integer Overflow vulnerability in PHP.
The vulnerability is due to a numeric error in the application when handling malicious requests. A remote attacker may be able exploit this via crafted requests to execute arbitrary codes with the current privileges of the running web server.
PHP Group PHP prior to 7.0.6
-System Compromise: Remote attackers can execute arbitrary code within the context of a targeted web server.
Apply the most recent upgrade or patch from the vendor.