Yii2 When Validation - yii2

Question

Out of two pairs of input fields I only need one or the other. I can't get the validation right.
listing_image_url and poster_image_url should only be required if $model->listingImage is null.
Also tried using strlen($model->listingImage) == 0.
[['listing_image_url', 'poster_image_url'], 'required',
'when' => function($model){
var_dump($model->listingImage); //result is empty string '0'
return $model->listingImage == NULL && $model->posterImage == NULL;
},'whenClient' => "function(attribute, value) {
return $('#vod-listingimage').val() == '' && $('#vod-posterimage').val() == '';
}", 'message' => 'look'
],
Just as above but the other way around.
[['listingImage', 'posterImage'], 'required',
'when' => function($model) {
return $model->listing_image_url == NULL && $model->poster_image_url == NULL;
},
'whenClient' => "function(attribute, value) {
return $('#vod-listing_image_url').val() == '' && $('#vod-poster_image_url').val() == '';
}", 'message' => 'hi'
],

Answer 1

You could create your own inline validator for the model validation on backend side, like this:
[['listingImage', 'posterImage'], function($attribute, $params) {
if ($this->listingImage === null && empty($this->$attribute)) {
$this->addError($attribute, 'Can not be blank if listingImage is null');
}
}]
In order to also provide the client side validation you can build a custom standalone validator.

Answer 2

I tried myself something similar and the behavior is odd indeed.
But you can create a validator that checks if only one of the two fields is selected.
public function validateListingAgainstPoster($attribute, $params)
{
if (!empty($this->listing_image_url) && !empty($this->poster_image_url)) {
$this->addError($attribute, 'Only one of "Listing" or "Poster" fields can be selected.');
}
if (empty($this->listing_image_url) && empty($this->poster_image_url)) {
$this->addError($attribute, 'Please select one of "Listing" or "Poster Group".');
}
}
And in your rules:
[['listing_image_url', 'poster_image_url'], 'validateListingAgainstPoster', 'skipOnEmpty' => false, 'skipOnError' => false],