<?php

$a = 'aaa' + 'bbb';
$b = 0 + '0ccc';
$c = 0 + 1;
$d = '0' + '1';


$e = 'eee' . 'fff';
$f = 'eee' . 'ffff' + 3;
$g = 'eee' . 3 + 3;
$h = 3 + 3 . 'kkk';
$j = 3 . 3 . 'xxx';

$k = $a . 3 + 'lll';