PHPオブジェクトプログラミングでバグが発生しました!

    public function insert(Array $c, $p = 'INSERT') {        if(!is_null($this->px)) return $this;        function i( $c, $e = ',') {            $d = '';            foreach ($c as $val) {                # code...                $d .= $e . '(';                foreach ($val as $valTow) {                    $d .= '"' . $valTow . '",';                    $d = trim($d, ',');                }                                // var_dump($d);                $d      .= ')';             }            return rtrim($d, ')');        }        $n = '(';        $d = '(';        foreach ($c as $key => $value) {            $n .= '`' . $key . '`,';            if(is_array($value)) {                $d = i($value);            } else {                $d .= '"' . $value . '",';            }        }        $n      = rtrim($n, ',') . ')';        $d      = rtrim($d, ',)');        $d      .= ')';                $this->insert = $p . ' INTO ' . $this->tableName . " {$n} VALUES {$d} ";        $this->px = __METHOD__;        return $this;    }