HTMLForm

<?php

class SpecialTestForm extends SpecialPage {
	public function __construct() {
		parent::__construct( 'TestForm' );
	}

	public function execute( $par ) {
		$this->getOutput()->setPageTitle( 'Test form' );

		$formDescriptor = [
			'myfield1' => [
				'section' => 'section1/subsection',
				'label-message' => 'testform-myfield1',
				'type' => 'text',
				'default' => 'Meep',
			],
			'myfield2' => [
				'section' => 'section1',
				'class' => 'HTMLTextField', // HTMLTextField same as type 'text'
				'label-message' => 'testform-myfield2',
			],
			'myfield3' => [
				'class' => 'HTMLTextField',
				'label' => 'Foo bar baz',
			],
			'myfield4' => [
				'class' => 'HTMLCheckField',
				'label' => 'This be a pirate checkbox',
				'default' => true,
			],
			'omgaselectbox' => [
				'class' => 'HTMLSelectField',
				'label' => 'Select an oooption',
				'options' => [
					'Pirates' => 'pirate',
					'Ninjas' => 'ninja',
					'Back to the NINJAR!' => 'ninjars',
				],
			],
			'omgmultiselect' => [
				'class' => 'HTMLMultiSelectField',
				'label' => 'Weapons to use',
				'options' => [
					'Cannons' => 'cannon',
					'Swords' => 'sword',
				],
				'default' => [ 'sword' ],
			],
			'radiolol' => [
				'class' => 'HTMLRadioField',
				'label' => 'Who do you like?',
				'options' => [
					'Pirates' => 'pirates',
					'Ninjas' => 'ninjas',
					'Both' => 'both',
				],
				'default' => 'pirates',
			],
		];

		$htmlForm = new HTMLForm( $formDescriptor, $this->getContext() );
		$htmlForm
			->setSubmitText( 'Foo submit' )
			->setSubmitCallback( [ $this, 'trySubmit' ] )
			->show();
	}

	public function trySubmit( $formData ) {
		if ( $formData[ 'myfield1' ] === 'Fleep' ) {
			return true;
		}

		return 'Fail';
	}
}

$wgSpecialPages['TestForm'] = 'SpecialTestForm';

$htmlForm = HTMLForm::factory( 'ooui', $formDescriptor, $this->getContext() );