FormTestPatternForm.php

<?php

namespace Drupal\form_test\Form;

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

/**
 * Builds a simple form using the FAPI #pattern property.
 *
 * @internal
 */
class FormTestPatternForm extends FormBase {
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'form_test_pattern_form';
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state) {
        $form['textfield'] = [
            '#type' => 'textfield',
            '#title' => 'One digit followed by lowercase letters',
            '#pattern' => '[0-9][a-z]+',
        ];
        $form['tel'] = [
            '#type' => 'tel',
            '#title' => 'Everything except numbers',
            '#pattern' => '[^\\d]*',
        ];
        $form['password'] = [
            '#type' => 'password',
            '#title' => 'Password',
            '#pattern' => '[01]+',
        ];
        $form['url'] = [
            '#type' => 'url',
            '#title' => 'Client side validation',
            '#description' => 'Just client side validation, using the #pattern attribute.',
            '#attributes' => [
                'pattern' => '.*foo.*',
            ],
            '#pattern' => 'ignored',
        ];
        $form['submit'] = [
            '#type' => 'submit',
            '#value' => 'Submit',
        ];
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
    }

}