Using kint() or dump() to inspect form arraysfor Drupal 8 , 9 , 10 , and 11

As you delve deeper into Drupal form development, understanding how to effectively debug and inspect form arrays becomes crucial. Tools like kint() and dump() are essential for examining these arrays, enabling developers to visualize data structures and debug their forms more efficiently.

Introducing kint() and dump()

In Drupal, kint() is part of the Devel module, providing a powerful debug display by formatting arrays and objects in a structured and human-readable manner. dump() is also available in the Symfony framework and offers a quick way to output variable content for inspection, albeit in a less formatted style than kint().

Both these functions are invaluable for developers who need to verify form structures and data flows, particularly when dealing with complex forms or troubleshooting unexpected behaviors.

Using kint() and dump() in Drupal Form Arrays

Step 1: Preparing Your Environment

Before employing kint(), ensure the Devel module is installed and enabled:

composer require drupal/devel

After installation, enable the module through the Drupal interface or by using Drush:

drush en devel 

Step 2: Implementing kint() in Form Debugging

Let’s utilize kint() to inspect a form array. Insert a simple kint() call within the form-building process:

// In src/Form/InspectForm.php
namespace Drupal\my_module\Form;

use Drupal\Core\Form\FormBase;
use Drupal\Core\Form\FormStateInterface;

class InspectForm extends FormBase {

    public function getFormId() {
        return 'inspect_form';
    }

    public function buildForm(array $form, FormStateInterface $form_state) {
        $form['example'] = [
            '#type' => 'textfield',
            '#title' => $this->t('Example Textfield'),
        ];
        $form['submit'] = [
            '#type' => 'submit',
            '#value' => $this->t('Submit'),
        ];

        // Use kint() to inspect the form array.
        kint($form);

        return $form;
    }

    public function submitForm(array &$form, FormStateInterface $form_state) {
        drupal_set_message($this->t('Form submitted successfully!'));
    }

}

Access the form in your browser, then inspect the output. The kint() call will display a formatted, interactive view of the form array, aiding in identifying every element and its properties.

Step 3: Employing dump()

Alternatively, you can use dump() for quick inspections:

dump($form); // Add this within your form functions as needed.

Note that dump() does not auto-format its output like kint(), making it less readable for larger structures.

When to Use kint() and dump()

• Complex Forms: Use these tools when debugging forms with many nested elements or custom conditions.
• Data Flow Verification: Verify that user inputs are processed and stored correctly within the form array.
• Development & Debugging: Ideal for development environments, where observing real-time changes in form structures can expedite development and troubleshooting.

Conclusion

By using kint() and dump(), developers gain insight into form structures and data flows, enabling them to diagnose issues and understand their applications better. Regularly employing these debugging tools is an essential best practice in form creation and manipulation.

In the next lesson, you will learn about logging validation failures for troubleshooting, which helps maintain the integrity and reliability of your forms by documenting issues for easy analysis and fixes.