Basically, you first want to check the input has the data you're looking for, if it does, try to process/validate it, if it validates, then use it in your query.

// Get the query builder instance for the model
$query = Model::query();

if (Input::has('start_at'))
{
    try {
        $start_at = Carbon::createFromFormat('d/m/Y', Input::get('start_at'));
    } catch(Exception $e) {
        // Carbon failed to process input
    }

    if (isset($start_at))
    {
        $query->where('created_at', '>=', $start_at);
    }
}

if (Input::has('end_at'))
{
    try {
        $end_at = Carbon::createFromFormat('d/m/Y', Input::get('end_at'));
    } catch(Exception $e) {
        // Carbon failed to process input
    }

    if (isset($end_at))
    {
        $query->where('created_at', '<=', $end_at);
    }
}

$results = $query->get();

hi iWader, thank you for the replay

I've 4 input that could affect the query, like if the date is isset and name is isset, then i will want to query the date between which has name of someone. In more deep i will have date between, name and instructor. I will have these in one page to see the result :

1. date between (start and end)
2. name of student
3. instructor
4. class
   if i choose only the date between, so i will query all user, class and instructor
   if i choose date with name, i will want to query the spesific user with all of his instructor and class
   if i choose the date, name and instructor, i will want to query the spesific user with spesific instructor and all class
   or i can choose the class only to show all the user and all instructor, or i can choose the instructor only to show all user and all class and so on, can you please advice me the proper way to do this? thank you in avance