Description:
------------
I have tested in version Debian 9, PHP 7.0.33-0+deb9u1 and CentOS Linux release 7.6.1810, 7.2.14 


array_diff in first example show, that is no difference between arrays values

Test script:
---------------
$t1['c'] = 3;
$t1['i'] = 10;
$t1['iv'] = 10;

$t2['c'] = 3;
$t2['i'] = 10;
$t2['iv'] = 11;


var_dump(array_diff($t1,$t2));
var_dump(array_diff($t2,$t1));


Expected result:
----------------
array(1) {
  ["iv"]=>
  int(11)
}
array(1) {
  ["iv"]=>
  int(11)
}


Actual result:
--------------
array(0) {
}
array(1) {
  ["iv"]=>
  int(11)
}