Debug Kit

DebugKit provides a debugging toolbar and enhanced debugging tools for CakePHP applications. It lets you quickly see configuration data, log messages, SQL queries, and timing data for your application.


DebugKit is only intended for use in single-user local development environments. You should avoid using DebugKit in shared development environments, staging environments, or any environment where you need to keep configuration data and environment variables hidden.


By default DebugKit is installed with the default application skeleton. If you’ve removed it and want to re-install it, you can do so by running the following from your application’s ROOT directory (where composer.json file is located):

php composer.phar require --dev cakephp/debug_kit "~5.0"

Then, you need to enable the plugin by executing the following line:

bin/cake plugin load DebugKit


  • DebugKit.panels - Enable or disable panels for DebugKit. You can disable any of the standard panels by:

    // Before loading DebugKit
    Configure::write('DebugKit.panels', ['DebugKit.Packages' => false]);
  • DebugKit.includeSchemaReflection - Set to true to enable logging of schema reflection queries. Disabled by default.

  • DebugKit.safeTld - Set an array of whitelisted TLDs for local development. This can be used to make sure DebugKit displays on hosts it otherwise determines unsafe.

    // Allow e.g. or http://my-shop.local domains locally
    Configure::write('DebugKit.safeTld', ['dev', 'local', 'example']);
  • DebugKit.forceEnable - Force DebugKit to display. Careful with this, it is usually safer to simply whitelist your local TLDs. Example usage:

    // Before loading DebugKit
    Configure::write('DebugKit.forceEnable', true);

    You can also provide a callable:

    Configure::write('DebugKit.forceEnable', function() {
        return $_SERVER['REMOTE_ADDR'] === '';
  • DebugKit.ignorePathsPattern - Regex pattern (including delimiter) to ignore paths. DebugKit won’t save data for request URLs that match this regex. Defaults to null:

    // Ignore image paths
    Configure::write('DebugKit.ignorePathsPattern', '/\.(jpg|png|gif)$/');
  • DebugKit.ignoreAuthorization - Set to true to ignore Cake Authorization plugin for DebugKit requests. Disabled by default.

  • DebugKit.maxDepth - Defines how many levels of nested data should be shown in general for debug output. Default is 5. WARNING: Increasing the max depth level can lead to an out of memory error.:

    // Show more levels
    Configure::write('DebugKit.maxDepth', 8);
  • DebugKit.variablesPanelMaxDepth - Defines how many levels of nested data should be shown in the variables tab. Default is 5. WARNING: Increasing the max depth level can lead to an out of memory error.:

    // Show more levels
    Configure::write('DebugKit.variablesPanelMaxDepth', 8);

Database Configuration

By default DebugKit will store panel data into a SQLite database in your application’s tmp directory. If you cannot install pdo_sqlite, you can configure DebugKit to use a different database by defining a debug_kit connection in the Datasources variable in your config/app.php file. For example:

 * The debug_kit connection stores DebugKit meta-data.
'debug_kit' => [
    'className' => 'Cake\Database\Connection',
    'driver' => 'Cake\Database\Driver\Mysql',
    'persistent' => false,
    'host' => 'localhost',
    //'port' => 'nonstandard_port_number',
    'username' => 'dbusername',    // Your DB username here
    'password' => 'dbpassword',    // Your DB password here
    'database' => 'debug_kit',
    'encoding' => 'utf8',
    'timezone' => 'UTC',
    'cacheMetadata' => true,
    'quoteIdentifiers' => false,
    //'init' => ['SET GLOBAL innodb_stats_on_metadata = 0'],

You can safely remove the tmp/debug_kit.sqlite file at any point. DebugKit will regenerate it when necessary.

Toolbar Usage

The DebugKit Toolbar is comprised of several panels, which are shown by clicking the CakePHP icon in the bottom right-hand corner of your browser after DebugKit has been installed and loaded. Each panel is comprised of a panel class and view element. Typically, a panel handles the collection and display of a single type of information such as Logs or Request information. You can choose to view panels from the toolbar or add your own custom panels.

Each panel lets you look at a different aspect of your application:

  • Cache See cache usage during a request and clear caches.

  • Environment Display environment variables related to PHP + CakePHP.

  • History Displays a list of previous requests, and allows you to load and view toolbar data from previous requests.

  • Include View the included files grouped by type.

  • Log Display any entries made to the log files this request.

  • Packages Display the list of packages dependencies with their actual version and allow you to check for outdated packages.

  • Mail Display all emails sent during the request and allow to preview emails during development without sending them.

  • Request Displays information about the current request, GET, POST, Cake Parameters, Current Route information and Cookies.

  • Session Display the information currently in the Session.

  • Sql Logs Displays SQL logs for each database connection.

  • Timer Display any timers that were set during the request with DebugKit\DebugTimer, and memory usage collected with DebugKit\DebugMemory.

  • Variables Display View variables set in controller.

  • Deprecations Display deprecation warnings in a more readable and less disruptive format.

Using the History Panel

The history panel is one of the most frequently misunderstood features of DebugKit. It provides a way to view toolbar data from previous requests, including errors and redirects.

Screenshot of the history panel in debug kit.

As you can see, the panel contains a list of requests. On the left you can see a dot marking the active request. Clicking any request data will load the panel data for that request. When historical data is loaded the panel titles will transition to indicate that alternative data has been loaded.

Using The Mail Panel

The mail panel allow you to track all emails sent during a request.

The mailer preview allows you to easily check emails during development.

Creating Preview Classes

In order to preview emails before sending them, you need to create a preview class that defines the receipient and required template variables for your mailer methods:

// in src/Mailer/Preview/WelcomePreview.php
namespace App\Mailer\Preview;

use DebugKit\Mailer\MailPreview;

class WelcomePreview extends MailPreview
    public function welcome()
        $mailer = $this->getMailer('Welcome');
        // set any template variables receipients for the mailer.

        return $mailer;

MailPreview classes should live in the Mailer\Preview namespace of your application or plugin, and use the Preview class suffix.

Developing Your Own Panels

You can create your own custom panels for DebugKit to help in debugging your applications.

Creating a Panel Class

Panel Classes simply need to be placed in the src/Panel directory. The filename should match the classname, so the class MyCustomPanel would be expected to have a filename of src/Panel/MyCustomPanel.php:

namespace App\Panel;

use DebugKit\DebugPanel;

 * My Custom Panel
class MyCustomPanel extends DebugPanel

Notice that custom panels are required to extend the DebugPanel class.


By default Panel objects have two callbacks, allowing them to hook into the current request. Panels subscribe to the Controller.initialize and Controller.shutdown events. If your panel needs to subscribe to additional events, you can use the implementedEvents() method to define all of the events your panel is interested in.

You should refer to the built-in panels for some examples on how you can build panels.

Panel Elements

Each Panel is expected to have a view element that renders the content from the panel. The element name must be the underscored inflection of the class name. For example SessionPanel has an element named session_panel.ctp, and SqllogPanel has an element named sqllog_panel.ctp. These elements should be located in the root of your src/Template/Element directory.

Custom Titles and Elements

Panels should pick up their title and element name by convention. However, if you need to choose a custom element name or title, you can define methods to customize your panel’s behavior:

  • title() - Configure the title that is displayed in the toolbar.

  • elementName() - Configure which element should be used for a given panel.

Panel Hook Methods

You can also implement the following hook methods to customize how your panel behaves and appears:

  • shutdown(Event $event) This method typically collects and prepares the data for the panel. Data is generally stored in $this->_data.

  • summary() Can return a string of summary data to be displayed in the toolbar even when a panel is collapsed. Often this is a counter, or short summary information.

  • data() Returns the panel’s data to be used as element context. This hook method lets you further manipulate the data collected in the shutdown() method. This method must return data that can be serialized.

Panels in Other Plugins

Panels provided by plugins work almost entirely the same as other plugins, with one minor difference: You must set public $plugin to be the name of the plugin directory, so that the panel’s Elements can be located at render time:

namespace MyPlugin\Panel;

use DebugKit\DebugPanel;

class MyCustomPanel extends DebugPanel
    public $plugin = 'MyPlugin';

To use a plugin or app panel, update your application’s DebugKit configuration to include the panel:

// in src/Application.php bootstrap() method add
Configure::write('DebugKit.panels', ['App', 'MyPlugin.MyCustom']);
$this->addPlugin('DebugKit', ['bootstrap' => true]);

The above would load all the default panels as well as the AppPanel, and MyCustomPanel panel from MyPlugin.

Accessing Toolbar without a frontend

If you have an application which only provides an API (and therefore no frontend) the usual way of accessing the toolbar can’t be used.

Instead you have to call http://localhost/debug-kit/toolbar/<debugkit-id>

The <debugkit-id> can be found inside the HTTP headers of your API response. It should look something like that:

X-DEBUGKIT-ID: 5ef39604-ad5d-4ca4-85d8-8595e52373bb

So you would have to call http://localhost/debug-kit/toolbar/5ef39604-ad5d-4ca4-85d8-8595e52373bb

Helper Functions

  • sql() Dumps out the SQL from an ORM query.

  • sqld() Dumps out the SQL from an ORM query, and exits.

Tracing query execution

Sometimes you need to know where specific queries are being executed in your app. To get this kind of information you can add the SqlTraceTrait to your Table class like so:

use DebugKit\Model\Table\SqlTraceTrait;

class CategoriesTable extends Table
    use SqlTraceTrait;

This will add the following information to the SQL log:

/* APP/Controller/CategoriesController.php (line 20) */