Print values organized

Speak, all right? I have this code, I would like to know how I can print the values, just one underneath the other and each one inside a respective box.

<?php

$a= [1,4,6,9,10,12]; 
$b= [2,4,9,12];

$iguais = [];
$diferentes = [];
foreach($a as $item){
    $i = array_search($item, $b);
    if($i !== false){
        $iguais[] = '('. $item .', '. $b[$i] .')';
        unset($b[$i]);
    }else{
        $diferentes[] = $item;
    }
}

$d = [$b];
$e = [$diferentes];

$common = array_intersect( $diferentes, $b,$a); 

$diff2 = array_diff( $b, $common );
$diff3 = array_diff( $diferentes, $common );

$diferentes += $b;

echo "IGUAIS - ";
print_r($iguais);

echo "FALTA PERNA EM CREDITO - ";
print_r($diff3);

echo "SOMA(a) = ".array_sum($diff3)."\n";

echo "FALTA PERNA EM DEBITO - ";
print_r($diff2);

echo "SOMA(a) = ".array_sum($diff2)."\n";

?>

Thank you for your attention.