PHP date_sub. can't substract today and date -

i trying output number of days between today , date enter have problem encounter error: "warning: date_diff() expects parameter 2 datetimeinterface" what's problem ?

<?php    $today=date("y-m-d");  $date=date_create("2016-09-16");    echo date_diff($date,$today);    ?>

your problem lies in when using date_diff have make sure you're comparing objects actual date objects. return type date_diff dateinterval object. you're treating string.

$today = new datetime(); // $today datetime object $date = new datetime("2016-09-16"); // $date datetime object! $diff =  date_diff($date,$today); // compare 2 objects of same type ftw!  echo $diff->days; // $diff dateinterval object, echo it's 'days' property.  // output: 3 (as of writing) 

further reading:
http://php.net/manual/en/class.dateinterval.php
http://php.net/manual/en/class.datetime.php
http://php.net/manual/en/function.date-diff.php