Question

I received the following error message when I tried to submit the content to my form. How may I fix it?

Notice: Undefined index: filename in D:\wamp\www\update.php on line 4

Example Update.php code:

<?php

    $index = 1;
    $filename = $_POST['filename'];

    echo $filename;
?>

And $_POST[‘filename’] comes from another page:

<?php
    $db = substr($string[0],14) . "_" . substr($string[1],14) . "_db.txt";
?>

<input type="hidden" name="filename" value="<?php echo $db; ?>">

Answer 1

Assuming you only copy/pasted the relevant code and your form includes <form method="POST">

---

if(isset($_POST['filename'])){
    $filename = $_POST['filename'];
}
if(isset($filename)){ 
    echo $filename;
}

If _POST is not set the filename variable won’t be either in the above example.

An alternative way:

$filename = false;
if(isset($_POST['filename'])){
    $filename = $_POST['filename'];
 } 
    echo $filename; //guarenteed to be set so isset not needed

In this example filename is set regardless of the situation with _POST. This should demonstrate the use of isset nicely.

More information here:
http://php.net/manual/en/function.isset.php