function get_daydiff($end_date,$today)
{
if($today=='')
{
$today=date('Y-m-d');
}
$str = floor(strtotime($end_date)/(60*60*24)) - floor(strtotime($today)/(60*60*24));
return $str;
}
$d1 = "2018-12-31";
$d2 = "2018-06-06";
echo get_daydiff($d1, $d2);