$time = strtotime('2016-03-24 03:25:43');
echo date('Y-m-d H:i:s');
echo ' event happened '.humanTiming($time).' ago';
 
function humanTiming ($time)
{
 
    $time = time() - $time; // to get the time since that moment
    $time = ($time<1)? 1 : $time;
    $tokens = array (
        31536000 => 'year',
        2592000 => 'month',
        604800 => 'week',
        86400 => 'day',
        3600 => 'hour',
        60 => 'minute',
        1 => 'second'
    );
 
    foreach ($tokens as $unit => $text) {
        if ($time < $unit) continue;
        $numberOfUnits = floor($time / $unit);
        return $numberOfUnits.' '.$text.(($numberOfUnits>1)?'s':'');
    }
 
}