error_reporting = E_ALL

display_errors = OFF

display_startup_errors = On

; 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

....

; Log errors to specified file. Esempio:
error_log = "c:/php_errorLog/php_error_log.txt"

La cartella ed il file devono esistere. Restarta apache.