if if语句为PHP DateTime diff

Question

I am using meta_box value (YmdHi) and current Date&time to print time difference. And this code work for me.

Now additionally i want to print Live when 2 hours left to start Event.

What mistake I 'm doing to print if or else currently this not work for me?

$then = date( get_post_meta( get_the_ID(), '_start_eventtimestamp', true ) ) ;
$then = new DateTime($then);
$now = new DateTime();
$sinceThen = $then->diff($now);

if ($sinceThen > 2 * HOUR_IN_SECONDS){
       echo $sinceThen->d.'days'; 
       echo $sinceThen->h.'hours'; 
       echo $sinceThen->i.'minutes';
 }
else{
        echo 'LIVE';
 }

Answer 1

$sinceThen is a DateInterval (that's what DateTime::diff() returns), so you're comparing a int with an object, which obviously gives you unexpected results. To get the difference in seconds, subtract both DateTime instances' timestamps (which you obtain with DateTime::getTimestamp()):

$then = date( get_post_meta( get_the_ID(), '_start_eventtimestamp', true ) ) ;
$then = new DateTime($then);
$now = new DateTime();
$sinceThen = $then->diff($now);
$sinceThenInSeconds = $then->getTimestamp() - $now->getTimestamp();

if ($sinceThenInSeconds > 2 * HOUR_IN_SECONDS){
    echo $sinceThen->d.'days'; 
    echo $sinceThen->h.'hours'; 
    echo $sinceThen->i.'minutes';
}
else{
    echo 'LIVE';
}