This indicates an attack attempt to exploit a Denial Of Service vulnerability in PHP.
The vulnerability is due to an error in the application when handling CDF files. A remote attacker may be able exploit this to cause a denial of service condition in the affected application.
PHP Group PHP prior to 5.6.0
PHP Group PHP prior to 5.5.16
PHP Group PHP prior to 5.4.32
Denial of Service: Remote attackers can crash vulnerable systems.
Apply the most recent upgrade or patch from the vendor