php - Skip Submit button in array_keys

I've got a PHP routine that processes a form and outputs the values to a CSV file. I'm using array_keys() to create the header row (skipped if there is one). Everything works perfectly except the final header term is "submit" because, of course, my form includes a Submit button. So the data ends up looking like this:

name,email,cell,dob,study,submit
"Temp One",fred@gmail.com,646-325-1111,1995-03-31,8,Submit
"Temp Two",tom@gmail.com,646-325-2222,1995-03-31,4,Submit

How do I omit the submit button both from the header and the data?

Here's my code:

if(isset($_POST['submit'])) {
    $data = array_values($_POST); // get only values
    $headers = array_keys($_POST); // keys are headers 
    if( $fp = fopen('data.csv','a+')) {
        $line = fgets($fp);

        if(!$line == $headers) {
                fputcsv($fp, $headers);
                fputcsv($fp, $data);
        }
        else
        {
            fputcsv($fp, $data);
        }
        fclose($fp);
        header('Location: thanks.php'); 

    }
}

Answer

Remove it from the array...

$post = $_POST;
unset($post['submit']);
$data = array_values($post); // get only values
$headers = array_keys($post); // keys are headers