Get youtube code from any URI

StringUtility.php

<?php
namespace In2code\In2template\Migration\Utility;

/**
 * Class StringUtility
 */
class StringUtility
{

    /**
     * Parse every kind of Youtube URI and return video code
     *
     *  Example URI:
     *      http://www.youtube.com/embed/6FjfewWAGdE?feature=player_detailpage
     *      http://www.youtube.com/embed/6FjfewWAGdE?feature=player_detailpage
     *      https://www.youtube.com/embed/6FjfewWAGdE
     *      https://youtube.com/embed/6FjfewWAGdE
     *      http://www.youtube.com/watch?v=6FjfewWAGdE
     *      http://www.youtube.com/watch?v=6FjfewWAGdE&feature=player_detailpage
     *      www.youtu.be/6FjfewWAGdE
     *      youtu.be/6FjfewWAGdE
     *      youtube.com/watch?v=6FjfewWAGdE
     *      https://www.youtube.com/watch?v=6FjfewWAGdE&feature=youtu.be
     *
     * @param string $uri
     * @return string
     */
    public static function getYoutubeCodeFromUri(string $uri): string
    {
        $code = '';
        $regExp = '~^(http://|https://|.*?)(www.|.*?)(youtube.com|youtu.be)/(embed/|watch\?v=|.*?)(.*?)(\?|\&|$)~';
        preg_match($regExp, $uri, $result);
        if (!empty($result[5])) {
            $code = $result[5];
        }
        return $code;
    }
}

improved regular expression:

$regExp = '~^(http://|https://)?(www\.)?(youtube\.com|youtu\.be)/(embed/|watch\?v=)?(?P<code>.*?)(\?|\&|$)~';
preg_match($regExp, $uri, $result);
if (!empty($result['code'])) {
    $code = $result['code'];
}

TestCase:

<?php
namespace In2code\In2template\Tests\Unit\Migration\Utility;

use In2code\In2template\Migration\Utility\StringUtility;
use TYPO3\TestingFramework\Core\Unit\UnitTestCase;

/**
 * Class StringUtility
 */
class StringUtilityTestCase extends UnitTestCase
{
    /**
     * @return array
     */
    public function getYoutubeCodeFromUriReturnsExpectedCodeDataProvider()
    {
        return [
            'http://www.youtube.com/embed/6FjfewWAGdE?feature=player_detailpage' => [
                'http://www.youtube.com/embed/6FjfewWAGdE?feature=player_detailpage',
                '6FjfewWAGdE'
            ],
            'https://www.youtube.com/embed/6FjfewWAGdE' => [
                'https://www.youtube.com/embed/6FjfewWAGdE',
                '6FjfewWAGdE'
            ],
            'https://youtube.com/embed/6FjfewWAGdE' => [
                'https://youtube.com/embed/6FjfewWAGdE',
                '6FjfewWAGdE'
            ],
            'http://www.youtube.com/watch?v=6FjfewWAGdE' => [
                'http://www.youtube.com/watch?v=6FjfewWAGdE',
                '6FjfewWAGdE'
            ],
            'http://www.youtube.com/watch?v=6FjfewWAGdE&feature=player_detailpage' => [
                'http://www.youtube.com/watch?v=6FjfewWAGdE&feature=player_detailpage',
                '6FjfewWAGdE'
            ],
            'www.youtu.be/6FjfewWAGdE' => [
                'www.youtu.be/6FjfewWAGdE',
                '6FjfewWAGdE'
            ],
            'youtu.be/6FjfewWAGdE' => [
                'youtu.be/6FjfewWAGdE',
                '6FjfewWAGdE'
            ],
            'youtube.com/watch?v=6FjfewWAGdE' => [
                'youtube.com/watch?v=6FjfewWAGdE',
                '6FjfewWAGdE'
            ],
            'https://www.youtube.com/watch?v=6FjfewWAGdE&feature=youtu.be' => [
                'https://www.youtube.com/watch?v=6FjfewWAGdE&feature=youtu.be',
                '6FjfewWAGdE'
            ],
        ];
    }

    /**
     * @test
     * @dataProvider getYoutubeCodeFromUriReturnsExpectedCodeDataProvider
     */
    public function getYoutubeCodeFromUriReturnsExpectedCode($uri, $expected)
    {
        $this->assertSame($expected, StringUtility::getYoutubeCodeFromUri($uri));
    }
}