Wsrtjtyk

        public function actionCreate()

    {

        $model = new AcaClassSubjects();



        if ($model->load(Yii::$app->request->post()) && isset($_POST['AcaClassSubjects'])) {



        $model->attributes = $_POST['AcaClassSubjects'];

        for($i=0;$i<count($_REQUEST['AcaClassSubjects']['class_subject_subject_id']);$i++) :

            $model->class_subject_id = NULL;

            $model->isNewRecord = true;

            $model->class_subject_subject_id = $_POST['AcaClassSubjects']['class_subject_subject_id'][$i];

            $model->class_subject_class_group_id = $_POST['AcaClassSubjects']['class_subject_class_group_id'];

            $model->class_subject_class_id = $_POST['AcaClassSubjects']['class_subject_class_id'];

            $model->created_by = Yii::$app->getid->getId(); 

            $model->created_at = new yiidbExpression('NOW()');

            if($model->save()) {

                  Yii::$app->session->setFlash('green-'.$i, '<i class="fa fa-info-circle"></i> <b>Class:</b> '.AcaClassMaster::findOne($_POST['AcaClassSubjects']['class_subject_class_id'])->class_name.' for <b>Subject: </b>'.AcaSubjects::findOne($_POST['AcaClassSubjects']['class_subject_class_id'][$i])->subject_name.' is created successfully');

            } else {

                  Yii::$app->session->setFlash('red-'.$i, '<i class="fa fa-warning"></i> The combination of <b>Class:</b> '.AcaClassMaster::findOne($_POST['AcaClassSubjects']['class_subject_class_id'])->class_name.' and <b>Subject: </b>'.AcaSubjects::findOne($_POST['AcaClassSubjects']['class_subject_class_id'][$i])->subject_name.' has already been taken.');

            }   

        endfor;

    

            return $this->redirect(['index']);

        } else {

            return $this->render('create', [

                'model' => $model,

            ]);

        }

    }

<div class="col-xs-12 col-lg-12">

    <div class="<?php echo $model->isNewRecord ? 'box-success' : 'box-info'; ?> box view-item col-xs-12 col-lg-12">

        <div class="academic-subject-form">

            <?php $form = ActiveForm::begin([

                    'id' => 'academic-subject-form',

                    'enableAjaxValidation' => false,

                    'fieldConfig' => [

                        'template' => "{label}{input}{error}",

                    ],

            ]); ?>    





            <div class="col-xs-12 col-lg-12 no-padding">  

                <div id="root-container-id" class="col-xs-12 col-sm-12 col-lg-12">   



                    <?=

                        $form->field($model, 'class_subject_subject_id')->checkboxList(AcaSubjects::forWidget(),[

                            'item' => function($index, $label, $name, $checked, $value) {

                                $checked = $checked ? 'checked' : '';

                                //'class' => 'check-all';

                                return "<label class='checkbox col-md-4' style='font-weight: normal;'><input type='checkbox' {$checked} name='{$name}' value='{$value}'>{$label}</label>";

                            }

                        ])->label('Subjects <label><input type="checkbox" id="root-container-id">Check All</label>');

                    ?>                                                  

                </div>

            </div>                       





            <div class="form-group col-xs-12 col-sm-6 col-lg-4 no-padding">

                <div class="col-xs-6">

                    <?= Html::submitButton($model->isNewRecord ? Yii::t('aca', 'Create') : Yii::t('app', 'Update'), ['class' => $model->isNewRecord  ? 'btn btn-block btn-success' : 'btn btn-block btn-info']) ?>

                </div>

                <div class="col-xs-6">

                    <?= Html::a(Yii::t('academic', 'Cancel'), ['index'], ['class' => 'btn btn-default btn-block']) ?>

                </div>

            </div>

            <?php ActiveForm::end(); ?>

        </div>

    </div>

</div>