How to get time difference using php

function nicetime($date)
{
if(empty($date)) {
return "No date provided";
}

$periods = array("second", "minute", "hour", "day", "week", "month", "year", "decade");
$lengths = array("60","60","24","7","4.35","12","10");

$now = time();
$unix_date = strtotime($date);

// check validity of date
if(empty($unix_date)) {
return "Bad date";
}

// is it future date or past date
if($now > $unix_date) {
$difference = $now - $unix_date;
$tense = "ago";

} else {
$difference = $unix_date - $now;
$tense = "from now";
}

for($j = 0; $difference >= $lengths[$j] && $j <>
$difference /= $lengths[$j];
}

$difference = round($difference);

if($difference != 1) {
$periods[$j].= "s";
}

return "$difference $periods[$j] {$tense}";
}

$date = "2009-10-07 14:00";
$result = nicetime($date);

echo $result;