Yii2: Show field/checkbox after checkbox is selected - checkbox

Question

I have an ActiveForm in my _form view:
<?php $form = ActiveForm::begin(); ?> <?= $form->field($model, 'isInternal')->checkbox() ?> <?php ActiveForm::end(); ?>
('isInternal' is a boolean)
If the checkbox is selected I want to show another checkbox:
$form->field($model, 'activateReminder')->checkbox();
Is there a possibility? Maybe with JavaScript like this?
<?= $form->field($model, 'isInternal')->checkbox(['onclick' =>
'showInternDetails()']) ?>
<script>
function showInternDetails() {
$model->isInternal = 1;
}
</script>
<?php
if($model->isInternal == true)
{
$form->field($model, 'activateReminder')->checkbox();
}
?>

Answer 1

You can do that by JS:
<?php
$this->registerJs(
"$('#myBox').on('change', function() { if($(this).is(":checked")){// Display your input...}else {// hide it} });",
View::POS_READY
);

Answer 2

You can use the when and whenClient options inside the model rules that you have declared so that it works when creating or updating both on the model end to require and show error to the user that he needs to select the value for the check-box and also to show and hide the activateReminder at the same time.
So go inside the model that you are using with this form and add a rule like below.
public function rules(){
return [
[['activateReminder'],'required','when'=>function($model){return ($model->isInternal);},
'whenClient'=>'function(attribute,value){
if($("#'.\yii\helpers\Html::getInputId($this, 'isInternal').'").val()===1){
$("#'.\yii\helpers\Html::getInputId($this, 'activateReminder').'").show();
return true;
}else{
$("#'.\yii\helpers\Html::getInputId($this, 'activateReminder').'").hide();
}
}']
];
}

Answer 3

Thank you for your answers!!
I have solved it as follows:
function isInternalOnClick(){
$('#isInternalCheckbox').on('change',function(){ showOrHideActivateReminder();});
}
function showOrHideActivateReminder() {
if($('#isInternalCheckbox').is(':checked'))
{
$('#hiddenActivateReminder').show()
}
else{
$('#hiddenActivateReminder').hide();
}
}
$(document).ready(function() {
<?php
if($model->isInternal)
{
echo "
showOrHideActivateReminder();
";
}
?>
});