Can't make multiple select in registration form - laravel

Question

I use the basic registration form but I want to add a multiple select, a User can have multiple Skills and select them when he register.
My problem is that when I select multiples values Laravel only take the last one, so I search on the web for a solution and they say to add [] after my class name, so this is what I do :
<div class="form-group row">
<div class="col-md-6">
<?php $competences = \App\Competence::all(); ?>
<select name="competences[]" multiple="" class="form-control">
<option value="" selected disabled style="display:none">choose your school</option>
#foreach ($competences as $competence)
<option value="{{ $competence->id }}">{{ $competence->name }}</option>
#endforeach
</select>
</div>
</div>
But now, when I submit the form the page reload and stay in the register form, and the user is not register... I don't know what to do, anyone of you have a solution ?
Here is how I check the competences in my registerController
$competences = $data['competences'];
foreach ($competences as $comp){
$user->competences()->save(Competence::find($comp));
}

Answer 1

Use multiple="multiple" OR just multiple in blade.php:
<div class="form-group row">
<div class="col-md-6">
<?php $competences = \App\Competence::all(); ?>
<select name="competences[]" class="form-control" multiple>
<option value="" selected disabled style="display:none">choose your school</option>
#foreach ($competences as $competence)
<option value="{{ $competence->id }}">{{ $competence->name }}</option>
#endforeach
</select>
</div>
</div>
then in your controller, verify that you're actually getting the data in the form of an array by just printing $data
return $data;