Filtering Syslog Messages

The syslog() function can be used to generate a log message that will be then processed by the operating system’s logger. A new configuration option, syslog.filter, was introduced in PHP 7.3 for optionally filtering these messages before they are passed on to the operating system’s logger:

Depending on how your operating system’s logger processes messages sent by PHP, appropriate filtering must be configured. Otherwise messages may become useless at best or a security risk at worst.