相关疑难解决方法(0)

我只是想知道如何使用变量名来在PHP中设置文件名？当我运行以下代码时:

<?php
if ($_POST) {
    $filename = $_POST['firstName'];

    header("Content-Type: application/txt");        
    header('Content-Disposition: attachment; filename="$filename.txt"');

    echo "Welcome, ";
    echo $_POST['firstName']. " " . $_POST['lastName'];

    exit;
} else {

?>

<form action="" method="post">
    First Name: <input type="text" name="firstName" /><br />
    Last Name: <input type="text" name="lastName" /><br />
    <input type="submit" name="submit" value="Submit me!" />
</form>

<?php } ?>

文件名总是被设置为" $filename.txt",但我想它是Adam.txt,或Brian.txt等根据用户的输入.