I want to print a message in post " After one month from publish date"

Question

I need to showing message in post , but after one month from publish date.

I try to make it before ask you, but I can't

this is my code

                $publish_date =  $post->post_date_gmt;
        $today = date('d-m-Y h:i:s');
        $nextMonth = mktime(0 , $publish_date('m')+1 , 0 , 0 , 0,0);
        echo 'Publish Date:'.$publish_date.'<br/>';
        echo 'Today Date:'.$today.'<br/>';
        echo 'Next Month:'.$nextMonth;
        if($today => $nextMonth){
            echo 'One Month or more for publish post';
        } else {
            echo '';
        }

Answer 1

Custom conditional I wrote for my theme (mostly to kick some widgets and ads from newer posts), works nicely:

function is_old_post( $days = 14 ) {

    if( !is_single() )
       return false;

    $id = get_the_ID();
    $date = get_post_field( 'post_date', $id );

    if( strtotime( $date ) < strtotime( "-{$days} days" ) )
        return true;

   return false;
}

Answer 2

Couple of things:

1. Your today date should have the format 'Y-m-d h:i:s'.
2. You might want to use current_time('mysql') instead, anyways (WP core function).

3. $publish_date('m')?, and mktime creates a unix timestamp, afaik, not a mysql one, which is what you're after, so instead of those, try this:

   $ts = strtotime($today);
   $m = date('m', $ts);
   $Y = date('Y', $ts);
   if ($m < 12) { $m++; } else { $m = 1; $Y++; }
   $nextMonth = date('Y-m-d', mktime( 0, 0, 0, $m, date('d', $ts), $Y ));