For the PHP Agent there is an agent log and a proxy log for each instrumented application.
Agent Log
The agent log is located at $<php_agent_install>/logs/agent.log. The log contains the transactions that the agent processes and then sends to the proxy.
The default pattern for agent log naming is the following:
agent.log: the current log
agent.log.1: most recent log
agent.log.2: second most recent log
agent.log.3: third most recent log
agent.log.4: fourth most recent log
agent.log.5: fifth recent log.
The agent creates and rotates a maximum of six log files. Maximum log size is 20 MB, which gives you a maximum of the most recent 120 MB of log data at one time.
Proxy Log
The proxy log is located $<php_agent_install>/logs/proxy_$date.log. This log contains the transactions that the proxy accepts from the agent and then sends to the Controller. See Proxy Logging and Dynamic Language Agent Proxy.