如何获取httpd进程用于PHP脚本的确切RAM量?

I want to run a PHP script and find out exactly how much RAM the httpd process that is running it is using. I have run a trace on the script with xdebug that shows me the script is using 3.9M. However when I run top, I see a lot of processes using 115M and more.

I'm not sure exactly what scripts are using how much RAM. I have access to the Apache status page, which doesn't show me the RAM the processes are using.

How can I run a PHP script and see exactly how much RAM the resulting httpd process is using?