怎样用php实现两个时间相减，得到相差的天数

最简单的方法-->公式：
$days=abs((strtotime(date("Y-m-d"))-strtotime("xxxx-xx-xx"))/86400);

 

 

eg:
  $last_logon_sql   = "select time, id from a";
 $last_logon_query = tep_db_query($last_logon_sql);
 $last_logon_text='';
while($last_logon_array = tep_db_fetch_array($last_logon_query)) {
 $last_logon_text.='' . "\n";
 
 $logon_time           = tep_datetime_short($last_logon_array['time']);
 $rencently_logon_time = date("y-m-d",strtotime($logon_time));
 $last_logon_time = abs((strtotime(date("Y-m-d"))-strtotime($rencently_logon_time))/86400);
        
 if($last_logon_time <= 3){ 
 $last_logon_text.='
     '. $last_logon_array['id'].'
     '. $last_logon_array['time'].'
 
  ';
 }
}
  echo $last_logon_text;
 ?>