Inserting error messages

[Hoggy]

Hi all!

 

Im having a bit of trouble inserting an error message to stop a user from carrying on after not filling in a text field. I havent a clue what the code is to do it but this is what I want to make mandatory:

 

<p>

<label for="userid" class ="fixed_required">

User ID: </label>

<input type="text" name="userid"

id="userid" value = "

<?php

if(isset($_POST['userid']))

echo $_POST['userid'];

?>

"/>

</p>

 

I want to make sure that a user has to have all fields filled in before they submit it and if they dont, have an error message pop up telling them to fill in required fields or something along those lines. Can anyone help me please?

[MatthewJ]

If you want to do it client side, check this link http://www.w3schools.com/js/js_form_validation.asp

 

or to do it server side http://www.onlamp.com/pub/a/php/2004/04/22/php_css_forms.html