fetchIds.php

<?php

if (isset($array)) {
    $videoID = [];
    $sql = "SELECT * FROM youtubelist ORDER BY id DESC LIMIT 5";
    $query = mysqli_query($sql);
    while ($youtubeData = mysqli_fetch_assoc($query)) {
        preg_match(
            '%(?:youtube(?:-nocookie)?\.com/(?:[^/]+/.+/|(?:v|e(?:mbed)?)/|.*[?&]v=)|youtu\.be/)([^"&?/ ]{11})%i',
            $youtubeData,
            $url);

        $videoID[] = $url[1];
    }

    echo json_encode($videoID);
}