if (!empty($form['first_contract_date']) && !empty($form['last_contract_date'])) {
    $first_contract_date_OBJ = DateTime::createFromFormat('d/m/Y', $form['first_contract_date']);
    $last_contract_date_OBJ = DateTime::createFromFormat('d/m/Y', $form['last_contract_date']);



    $contract_date_interval = $first_contract_date_OBJ->diff($last_contract_date_OBJ, true);
    $form['total_contract_day'] = $contract_date_interval->format('%a');


    }

    $form['total_test_event_contract_day'] = '';
    // calcul d'intervalles
    if (!empty($form['test_event_first_contract_date']) && !empty($form['test_event_last_contract_date'])) {
    $test_event_first_contract_date_OBJ = DateTime::createFromFormat('d/m/Y', $form['test_event_first_contract_date']);
    $test_event_last_contract_date_OBJ = DateTime::createFromFormat('d/m/Y', $form['test_event_last_contract_date']);

    $test_event_contract_date_interval = $test_event_first_contract_date_OBJ->diff($test_event_last_contract_date_OBJ, true);
    $form['total_test_event_contract_day'] = $test_event_contract_date_interval->format('%a');

    }
    exit();