function elapsed_time ( $start, $end = false)
{
if ($end == false) //if you don't pass a second parameter,
$end = time(); //we assume you're comparing to now.

$diff = $end - $start;
$days = floor ( $diff/86400 ); //calculate the days
$diff = $diff - ($days*86400); // subtract the days

$hours = floor ( $diff/3600 ); // calculate the hours
$diff = $diff - ($hours*3600); // subtract the hours

$mins = floor ( $diff/60 ); // calculate the minutes
$diff = $diff - ($mins*60); // subtract the mins

$secs = $diff; // what's left is the seconds;
if ($secs > 0) {
$returnval = "$secs second".(($secs>1) ? "s":"")." ago";
}

if ($mins > 0) {
$returnval = "$mins minute".(($mins>1) ? "s":"")." ago";
}

if ($hours > 0) {
$returnval = "$hours hour".(($hours>1) ? "s":"")." ago";
}

if ($days > 0) {
$returnval = "$days day".(($days>1) ? "s":"")." ago";
}

$return = "About "; //change the wording to what you like
return $return . $returnval;
}