private function generateForeignKey($table)
    {
        if (empty($table->foreignKeys)) {
            return;
        }
        $definition = "// fk: $table->name\n";

        foreach ($table->foreignKeys as $fk) {
            $refTable = '';
            $refColumns = '';
            $columns = '';

            foreach ($fk as $k => $v) {
                if (0 === $k) {
                    $refTable = $v;
                } else {
                    $columns = $k;
                    $refColumns = $v;
                }
            }
            $definition .= sprintf("\$this->addForeignKey('%s', '{{%%%s}}', '%s', '{{%%%s}}', '%s');\n",
                'fk_'.$table->name.'_'.$columns, $table->name, $columns, $refTable, $refColumns);
        }
        return "$definition\n";
    }