# Method Sql.pgsql()->set_notify_callback()

Method set_notify_callback

  ``final` `void` set_notify_callback(`string` `condition`, `void`|`function`(`int`, `string`, `string`, `mixed` ... :`void`) `notify_cb`, `void`|`int` `selfnotify`, `mixed` ... `args`)`

Description

  With PostgreSQL you can LISTEN to NOTIFY events. This function allows you to detect and handle such events.

Parameter `condition`

  Name of the notification event we're listening to. A special case is the empty string, which matches all events, and can be used as fallback function which is called only when the specific condition is not handled. Another special case is `"_lost"` which gets called whenever the connection to the database unexpectedly drops.

Parameter `notify_cb`

  Function to be called on receiving a notification-event of condition `condition`. The callback function is invoked with `void notify_cb(pid,condition,extrainfo, .. args);` `pid` is the process id of the database session that originated the event. `condition` contains the current condition. `extrainfo` contains optional extra information specified by the database. The rest of the arguments to `notify_cb` are passed verbatim from `args`. The callback function must return no value.

Parameter `selfnotify`

  Normally notify events generated by your own session are ignored. If you want to receive those as well, set `selfnotify` to one.

Parameter `args`

  Extra arguments to pass to `notify_cb`.

Note

  This function is PostgreSQL-specific.