// Sample usage

$dateNow = getIsoDate();
$dateAgo = '2005-12-05 18:30:12';
echo howLongAgo($dateNow, $dateAgo);


function howLongAgo($dateNow, $dateAgo)
{
    $sDifference = '';
    $isRecent = true;

    $secondsDifference = (int) ( ( strtotime($dateNow) - strtotime($dateAgo) ) );
    $sDifference = $secondsDifference . ' seconds';
    if ($secondsDifference >= 60)
    {
        $minutesDifference = (int) ($secondsDifference / 60);
        $sDifference = $minutesDifference;
        $sDifference .= ($minutesDifference == 1) ? ' minute' : ' minutes';

        if ($minutesDifference >= 60)
        {
            $hoursDifference = (int) ($minutesDifference / 60);
            $sDifference = $hoursDifference;
            $sDifference .= ($hoursDifference == 1) ? ' hour' : ' hours';

            if ($hoursDifference >= 24)
            {
                $isRecent = false;
                $daysDifference = (int) ($hoursDifference / 24);
                $sDifference = $daysDifference;
                $sDifference .= ($daysDifference == 1) ? ' day' : ' days';

                if ($daysDifference >= 30)
                {
                    $monthsDifference = (int) ($daysDifference / 30);
                    $sDifference = $monthsDifference;
                    $sDifference .= ($monthsDifference == 1) ? ' month' : ' months');
                }
            }
        }
    }

    $sDifference .= ' ago';

    if ($isRecent) {
        $sDifference = '<span class="recent">' . $sDifference . '</span>';
    }

    return $sDifference;
}