inception.php

<?php

function inception($iterator = 1, $range = 0, $limit = 15, $goDeeper = true) {
    while ($iterator < $limit) {
        echo ($range += $iterator)%10;
        $goDeeper and inception($iterator, $range, ($limit - 1), false);
        ++$iterator;
    }
    print PHP_EOL;
};

inception();