阵列出现问题

我正在为excel创建一个导出工具，但我的数组有问题。

当我去打印时，我只看到A？

代码：

$num = $_POST['num'];
    for($i =0; $i< $num; $i++){
    $firstname =  $_POST['firstnameexport'];
    $lastname = $_POST['lastnameexport'];
    $email = $_POST['emailexport'];
    $phone = $_POST['phoneexport'];
    $data = array(
    array("firstname" => $firstname[$i] , "lastname" => $lastname[$i], "email" => $email[$i], "phone" => $phone[$i])
    );
    print_r($firstname[$i]);
    }

它会打印：

Afirstname  lastname    email   phone
A   A   A   A

值正在通过表单传递

这是代码：

$memberfirstnamearray  = array($j => $memberfirstname);
                                    $memberlastnamearray  = array($j => $memberlastname);
                                    $memberphonearray  = array($j => $memberphone);
                                    $memberemailarray  = array($j => $memberemail);
                                    $j++;
                                    $i++;

i和j在开始时为0

<input type='hidden' name='firstnameexport' value='$memberfirstnamearray' />
                                        <input type='hidden' name='lastnameexport' value='$memberlastnamearray' />
                                        <input type='hidden' name='emailexport' value='$memberphonearray' />
                                        <input type='hidden' name='phoneexport' value='$memberemailarray' />
                                        <input type='hidden' name='num' value='$j' />