Form Validation

fasterisbest

Hey guys,

Can anyone tell me how I would validate a form with PHP without actually leaving the page?

Let's say I have a form that asks for "name", "email" and "message". lets say the user does not fill in their name but they fill out the "email" field and the "message " field. Right now I have a piece of code that looks like this:


if(strlen($name)<3)
		{
		$errormsg = "Please enter your full name";
		header("Location: http://".$_SERVER['HTTP_HOST'].dirname($_SERVER['PHP_SELF'])."/email.php?errormsg=".$errormsg);
		exit;
		}

It finds the div with the ID "errormsg" thought the GET function and displays the message, HOWEVER.........It resets the form. So if someone has typed in a short story they lose their entire message.....annoying!

So, how do I go about informing the user that they did not fill out a field correctly with out reloading the page or reseting the form?

Thanks in advance for your help.

Piranha

Basically there are 3 ways to do it:

Use JavaScript to validate when the user clicks submit. Then you don't have to ever enter PHP until the result is good. Note that JavaScript could be turned off, if it is it would be no help at all.
Use AJAX. In this case I don't think it is a good idea, but it is a possibility.
Submit the form and, if something is wrong, print it back to the form. Something like below. Even if you choose to use one of the above you should use this as well, since the other need javascript activated.

<?php
if (isset($_POST['submitted'])) { // The form is sent
  $abc = $_POST['abc'];
  if ($abc == ok) {
    // Do something
  } else {
    // Continue with the form
  }
}
?>

<form method="post">
  <input type="text" name="abc" value="<?php echo $abc ?>"/>
  <input type="hidden" name="submitted" value="true"/>
  <input type="submit"/>
</form>