Multiple Submit buttons in Ajax

I cannot seem to get working to have multiple submit buttons on my page, actually I cannot get it working to read the value of the submitbutton in the controller. Once I can read it I can make it work

The form is posted through pjax and when the code enters the controller and I echo a complete post

print_r($_POST );

There is only the value of the form, not the name or value of the button I pressed

$PjaxSection ="transfer_preparation";

    echo Html::submitButton(Yii::t('app', 'audit'), [ 'name'=>'submitstep', 'value'=>'ADVANCED', 'class' => 'btn btn-xsmall', 'id'=>$PjaxSection.'_submitme']);  

$form = ActiveForm::begin([


        'action' =>['check_upload'] ,

         'method' => 'POST',

//        'enableAjaxValidation'=>false,


        'options' => ['class' => 'form-horizontal', 'enctype' => 'multipart/form-data',

        'data-pjax' => true,                    //PJAX



Any suggestions ?