test.php

<?php 

function showDiff($year, $month, $day)
{
    $sentence = [];
    $comma    = $this->translator->trans('diff.comma');
    $and      = $this->translator->trans('diff.and');

    if ($year) {
        $sentence[] = $this->translator->transChoice('diff.year', $year, array('year' => $year));
    }

    if ($month) {
        $sentence[] = $this->translator->transChoice('diff.month', $month, array('month' => $month));
    }

    if ($day) {
        $sentence[] = $this->translator->transChoice('diff.day', $day, array('day' => $day));
    }

    $last = array_pop($sentence);

    return implode($and, [implode($coma, $sentence), $last]);
}