为什么在 $_FILES["fname"]['name'] 中显示未定义索引错误；部分？

Question

    <?php 

$name= $_FILES['fname']['name'];
echo $name;


?>

<form action="test.php" method="POST" enctype=" multipart/form-data">
    Select file: <br><br>

    <input type="file" name="fname"><br><br>
    <input type="submit"><br>


</form>

Answer 1

<?php
if(isset($_POST["submit"])) {
$name= $_FILES['fname']['name'];
echo $name;
}

Answer 2

This file must be save as test.php     
 <?php 
    if(isset($_POST['formFile'])){
    $name= $_FILES['fname']['name'];
    echo $name;
    }
else{
echo "No file selected";
}

    ?>

    <form action="test.php" method="POST" enctype="multipart/form-data">
        Select file: <br><br>

        <input type="file" name="fname"><br><br>
        <input type="submit" name="formFile"><br>


    </form>

为什么在 $_FILES["fname"]['name'] 中显示未定义索引错误；部分？

why it is shown Undefined index error in the $_FILES["fname"]['name']; section?

php

arrays

undefined-index