Modal button Yii2

//js
<?php
$js = <<< JS
    $('#modalku').on('shown.bs.modal', function(event) {
        var button = $(event.relatedTarget);
        var url = button.attr('href');
        var title = button.attr('data-title');
        $('#modalContent').html('Loading content..');
        $('#modalHeader').html('<h4>'+title+'</h4>');
        $('#modalContent').load(url);

        return false;
    });
JS;
$this->registerJs($js, \yii\web\View::POS_READY);
?>

//button href
<?= Html::a('Tambah User Admin',
    ['add-user', 'id' => 1],
    [
        'class' => 'btn red',
        'data' => [
            'title' => 'Tambah User Admin',
            'toggle' => 'modal',
            'target' => '#modalku',
        ]
    ]
) ?>
<?= Html::a('Tambah User Mahasiswa',
    ['add-user', 'id' => 2],
    [
        'class' => 'btn blue',
        'data' => [
            'title' => 'Tambah User Mahasiswa',
            'toggle' => 'modal',
            'target' => '#modalku',
        ]
    ]
) ?>
<?= Html::a('Tambah User Dosen',
    ['add-user', 'id' => 3],
    [
        'class' => 'btn green',
        'data' => [
            'title' => 'Tambah User Dosen',
            'toggle' => 'modal',
            'target' => '#modalku',
        ]
    ]
) ?>

//modal
<?php
Modal::begin([
    'header' => '<div id="modalHeader"></div>',
    'id' => 'modalku',
    'options' => [
        'tabindex' => false
    ],
]);
    echo "<div id='modalContent'> </div>";
Modal::end();
?>