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Nut command / Debugging / Event Listeners

Note: You are currently reading the documentation for Bolt 3.6. Looking for the documentation for Bolt 3.5 instead?

Nut's debug:events command outputs configured event details such as name, listening function, and execution priority.

A note on priority numbers. The event dispatcher calls listening functions by name, in order of priority defined by the listener/subscriber.

Note: The default priority of listeners and subscribers is `0`.

Tip: The higher the number, the earlier the function will be called. So a callback function with the priority of `1` will be executed before `-1`.

Use cases

Debugging event listeners is usually for the following reasons:

  • Calculate your event listener's priority, to execute before, or after, another listener
  • Finding listeners that may be unexpectedly halting propagation of events, meaning that remaining listeners to that event are not being called, commonly due to Event::stopPropagation() having been called by a prior listener

Usage

    php .app/nut debug:events [options] [--] [<event>]

Running debug:events, without providing an event name, will output details on all events.

Arguments

Option Description
event An event name

Options

Option Description
--sort-listener Sort events in order of callable name
--names Summary list of the event names listened to

Example

Query Single Event

To check what is listening to the kernel.response event:

$ php ./app/nut debug:events kernel.response

Registered Listeners for "kernel.response" Event
================================================

+-------+----------------------------------------------------------------------------------+----------+
| Order | Callable                                                                         | Priority |
+-------+----------------------------------------------------------------------------------+----------+
|    #1 | Bolt\EventListener\FlashLoggerListener::onEvent()                                |     1000 |
|    #2 | Silex\EventListener\MiddlewareListener::onKernelResponse()                       |      128 |
|    #3 | Symfony\Component\HttpKernel\EventListener\ResponseListener::onKernelResponse()  |        0 |
|    #4 | Silex\Application {closure}                                                      |        0 |
|    #5 | Silex\EventListener\LogListener::onKernelResponse()                              |        0 |
|    #6 | Symfony\Component\HttpKernel\EventListener\SurrogateListener::onKernelResponse() |        0 |
|    #7 | Bolt\EventListener\GeneralListener::onResponse()                                 |        0 |
|    #8 | Bolt\EventListener\SnippetListener::onResponse()                                 |        0 |
|    #9 | Bolt\EventListener\RedirectListener::onResponse()                                |        0 |
|   #10 | Symfony\Component\HttpKernel\EventListener\ProfilerListener::onKernelResponse()  |     -100 |
|   #11 | Bolt\Session\SessionListener::onResponse()                                       |     -128 |
|   #12 | Bolt\EventListener\FlashLoggerListener::onEvent()                                |     1000 |
+-------+----------------------------------------------------------------------------------+----------+

Sort by Callable

To see the kernel.response events, sorted by the callable:

$ php ./app/nut debug:events kernel.response --sort-listener

Registered Listeners for "kernel.response" Event
================================================

+-------+----------------------------------------------------------------------------------+----------+
| Order | Callable                                                                         | Priority |
+-------+----------------------------------------------------------------------------------+----------+
|    #1 | Bolt\EventListener\FlashLoggerListener::onEvent()                                |     1000 |
|   #12 | Bolt\EventListener\FlashLoggerListener::onEvent()                                |     1000 |
|    #7 | Bolt\EventListener\GeneralListener::onResponse()                                 |        0 |
|    #9 | Bolt\EventListener\RedirectListener::onResponse()                                |        0 |
|    #8 | Bolt\EventListener\SnippetListener::onResponse()                                 |        0 |
|   #11 | Bolt\Session\SessionListener::onResponse()                                       |     -128 |
|    #4 | Silex\Application {closure}                                                      |        0 |
|    #5 | Silex\EventListener\LogListener::onKernelResponse()                              |        0 |
|    #2 | Silex\EventListener\MiddlewareListener::onKernelResponse()                       |      128 |
|   #10 | Symfony\Component\HttpKernel\EventListener\ProfilerListener::onKernelResponse()  |     -100 |
|    #3 | Symfony\Component\HttpKernel\EventListener\ResponseListener::onKernelResponse()  |        0 |
|    #6 | Symfony\Component\HttpKernel\EventListener\SurrogateListener::onKernelResponse() |        0 |
+-------+----------------------------------------------------------------------------------+----------+
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