Hi
Can you confirm if appdynamics_agent.ini is present in the directory where php.ini is present ?
Also make sure appdynamics_agent.so is present in the extension directory of the php installation.
You can also use 'php -i' command and examine the output. You should see appdynamics_agent.ini in it.
Note that PHP agent works with a Java Proxy process. Make sure this proxy is running (ps -ef | grep java).
Good luck.
Karun