aaa.php

    public function buildTestCases($variations) {
        $iterate = function($variations, $depth = 0, $indexies = []) use (&$iterate) {
            $keys = array_keys($variations);
            if ($depth >= count($keys)) {
                yield $indexies;
            } else {
                $key = $keys[$depth];
                for ($i = 0; $i < count($variations[$key]); $i++) {
                    $val = $variations[$key][$i];
                    $iterator = $iterate($variations, $depth + 1, array_merge($indexies, [$key => $val]));
                    foreach ($iterator as $variation) {
                        yield $variation;
                    }
                }
            }
        };

        $testCases = [];
        $no = 1;
        foreach ($iterate($variations) as $variation) {
            $title = $no++ . ".";

            $keys = array_keys($variation);
            $title = array_reduce($keys, function($title, $key) use ($variation) {
                $val = $variation[$key];
                return "{$title}　{$key}：{$val}";
            }, $title);

            $testCases = array_merge($testCases, [
                $title => [$variation]
            ]);
        }

        return $testCases;
    }