php date & time compare

Hi guys,
I'm working on a web project using php which has an
application form, and I need some help with
comparing dates.

Let's assume that I already have a function that
get the last date and time a user of a specific
ip address made a post. I basically want to limit
a user (based on their ip) to one (1) post
per day (24 hrs) or once every two days.

I just need help in creating a function
that can compare the two dates.

example

function can_post($lastPost, $now) {
'...
}

It would also be nice if I could tell when
is the next time that the can post.

thanks!

Try something like this:

<?
/* Last post was October 1, 2002 @ 5:10AM */
// mktime is as follows (hour, minute, second, month, day, year)
$lastpost = mktime(5,15,0,10,1,2002);

echo 'Last Post was: ', date("M-d-Y H:m:s a", $lastpost), '<br>';

if (canPost($lastpost, 24)) {
echo 'The time now is: ', date("M-d-Y H:m:s a", time()), '<br>';
print 'ok to post';
} else {
echo 'next post time is ', date("M-d-Y H:m:s a", $lastpost+(3600*24));
}


function canPost($lastpost, $diff)
{

// Lets turn hours into seconds
$diff = $diff*3600;

// When can the user post next?
$nextpost = $lastpost+$diff;

// What time is it now?
$timenow = time();


// Is the time now greater than the
// next available post time?
if ($timenow > $nextpost) {
return true;
} else {
return false;
}

}


?>

Thanks I'll give it a try