How to get days in Eloquent Query In Laravel

I want to find days between 2 dates in Eloquent Query In Laravel. I have Query Like this,

$credentials = Documents::whereIn('agency_id', $agency_ids)
                                ->with('dp_credential')
                                ->get()->toArray();

                if (count($credentials)) {
                    foreach ($credentials as $val) {
                        if ($val['dp_credential']) {
                            $current_date = new DateTime(date('Y-m-d'));
                            $expiry_date = new DateTime($val['dp_credential']['expiry_date']);
                            $interval = $current_date->diff($expiry_date);
                            $days = $interval->format('%r%a'); // if you getting days in minus then use %r
                            $val['dp_credential']['days'] = $days;
                            $val['dp_credential']['is_expiry'] = 0;
                            if ($days < 30) {
                                $val['dp_credential']['is_expiry'] = 1;
                            }
                         } }}

Eager Loading Relationship

public function dp_credential() {
    return $this->hasone('App\Model\ClinicianCredentials', 'document_type', 'id')
                    ->where('clinician_id', Auth::User()->id);
}

Now I Want to Find days without for each loop in eloquent query between the current date and dp_credential exist one date. and if days less than 30 then I want to add one extra key, is it possible without for each loop.

This works fine but I want this one without for each loop.

Sorry for my Poor English.

via Chebli Mohamed