PHP array delete by value (not key)

if (($key = array_search($produto->category, $categorias)) !== false) {
    unset($categorias[$key]);
}

<select name="category" class="form-control" required="">
    <option value="{{$produto->category}}" selected>{{$produto->category}} <small>(atual)</small> </option>
    @foreach($categorias as $cat)
    <option value="{{$cat}}">{{$cat}}</option>
    @endforeach
</select>