Display value from user input form

Question

I have this form which has 2 radio buttons. If I select the radio button labeled as one way, the return date and time will be invisible; if I select return, the return date and time will be visible. I just want to test if the data have been entered when oneway is selected. This is because when I select return, I can print out all the input values by user, but if I select oneway, I can't do so.

This is the code I am using.

echo "<h1>Booking</h1>";
$submit = $_POST['submit'];

if ($submit) {  
  // Check the direction selected by user.
  if ($direction == "return") {
    if ($liner && $direction && $from && $f_date && $f_time && $destination && $t_date && $t_time && $txttotal) {
      echo "$liner/$direction/$from /$f_date/$f_time/ $destination/$t_date/$t_time/$txttotal  ";
    }
  }
}

Answer 1

In the Drupal Examples project you can find the ajax_example module with a similar form with dependent fields.

http://drupal.org/project/examples

Answer 2

Please use the Drupal form API -- http://api.drupal.org/api/drupal/developer%21topics%21forms_api_reference.html/7

You should almost never use the $_POST / global PHP variables in Drupal communications as they are not sanitized.

To handle submitted content you should be using hook_form_submit(). The Devel module http://drupal.org/project/devel is very helpful in debugging / figuring out what data you are passing back and forth for processing.