How does error_log open the file?

I'm curious as to how error_log is opened... Is it opened when an error occurs, as in open/append to, or is the file handle kept open when the PHP fastcgi process is spawned? Essentially I want to be able to provide each client their own PHP error log, i.e. /home/client1/php-error.log But I have multiple webservers (3 of them currently) serving up PHP content. Can I point all 3 to that same place? Or will they try to issue locks and create a bunch of thrash? if it just creates/appends on each error instance that would be perfect. I am using php-fpm w/ 5.2.6, and NFS is used for central storage, mapped as /home to all the webservers. I figured you internals guys would know exactly how it works, I don't know C well enough to pick through the code and understand this fully. I think it's in main/main.c: fd = VCWD_OPEN_MODE(PG(error_log), O_CREAT | O_APPEND | O_WRONLY, 0644); From what I can tell. Although I don't know where to look to see if it persists, but I am thinking it is safe to assume every error that occurs triggers this php_log_err() function... any help is appreciated. Thanks, mike