Assuming you have SSH access to your server see if you etc\php.ini has this enabled.
; Log errors into a log file (server-specific log, stderr, or error_log (below))
; As stated above, you're strongly advised to use error logging in place of
; error displaying on production web sites.
log_errors = On
The default name if not specified is error_log.
If enabled it will write a error log.
Open a shell session and run this from the root of the drive file system.
[root@myserver /]# find -name error_log
This will find all error_log files.
Depending on your setup (plesk for example) will store the error_log under the sites folders.