Stimulate

$a = '
0
1
2
3
4
5
6
7
8
9';

$b = '
5
4
3
2
1';

foreach(explode("\r\n", $a) AS $a_item) {
    if ($a_item != '') {
        if (in_array($a_item, explode("\r\n", $b))) {
                echo '+'.$a_item."\r\n";
        }   
        else {
            echo '-'.$a_item."\r\n";
        }
    }
}

if (!$result) {
    printf("Errormessage: %s\n", mysqli_error($connect));
}

.box__item:nth-of-type(1) {
	background: red;
}