How to fix 'Notice: Undefined index:' in PHP form action

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">

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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

Answer 2

if(isset($_POST['form_field_name'])) {     $variable_name = $_POST['form_field_name']; }