<?php
$_POST_EXAMPLE = array();
$_POST_EXAMPLE['ratings'] = array(
'snickers' => 2,
'twix' => 1,
'butterfinger' => 3
);
$ratings = array_unique($_POST_EXAMPLE['ratings']);
// Two of the candy bars had the same rating
if( count($ratings) !== 3 ) {
echo 'ERROR MSG HERE!';
}else {
echo 'Success!';
}