xampp - Undefined Index for $_POST (noob question!)

I am just learning PHP and I keep getting an Undefined Index error. The book I'm learning from has an HTML form and a PHP page that processes the form, using the following format:

// The PHP starts with one line like this for each of the form fields in the HTML
$how_long = $_POST ['howlong'];

// And there is one line for each one like this to output the form data: 

echo ' and were gone for ' . $how_long . '
';

The example I'm working with has about 12 form fields.

What's odd is that not all of the variables throw this error, but I can't see a pattern to it.

I've checked that all HTML fieldnames match up with the PHP $_POST variable name I entered, and I've made certain that when I fill out the form and submit it that all fields are filled in with something. Interestingly, the completed code that can be downloaded for the book also throws this error.

I realize this code may not reflect best practices, it's from the first chapter of the book and obviously I am a noob :)

In case it makes a difference, I am using PHP 5.3.5 on XAMPP 1.7.4 with Windows 7 Home Premium.

Answer

Remember to set the method to POST on the form tag...

heres the code i used to try yours, and it worked to me:

in a file named test.php:

and in testProc.php:

if (isset($_POST)) {
  if (isset($_POST["howlong"])){
    $howlong = $_POST['howlong'];
    echo ' and were gone for ' . $howlong . '
';
  }
}
?>

Just as an advise, to make display manipulation with stylesheets i recommend to put forms within a table, like this:

  
    

      










        
          
            


              How long? :
            
            

              
            
          
          
                      
        
      
    
  

Hope you can use this...