我希望能够在webform上按下提交按钮后在同一页面上显示错误

i currently have a webform, programmed in html, and i have a php content handler, wich checks for errors, and does all what needz to be done, but i would love to show the errors if there are errors, on the webform page itself, i don't have a clue how to do this, but i could send my code.

Any help on this matter would be useful, thanks.

HTML DOC

Do you like the content on our website? Do you want to be a part of it? Want to earn more Karma?<br />
Do you have what it takes to be a content creator? Then sign up here!<br> <br>
<?php 
function getUID()
{
     global $user;
     if ($user->uid) 
     { 
          $userID=$user->uid;
          echo $userID;
     }
     else
    {
          header('Location: http://brokendiamond.org/?q=node/40');
    }
}
function getUN()
{
     global $user;
     if ($user->uid) 
     { 
          $username=$user->name;
     }
     echo $username;
}

?>
<form name="input" action="php-scripts/sendmail.php" method="post">
Username: &nbsp;&nbsp;&nbsp;&nbsp
<input type="hidden" name="UserID" value="<?php getUID() ?>">
<input type="text" name="username" value="<?php getUN() ?>" /><br>
E-mail adress: 
<input type="text" name="mail" /><br><br>
What type of 'Content Creator' do you want to become? <br />
<input type="radio" name="CCT" value="Blogger" /> Blogger<br />
<input type="radio" name="CCT" value="Livestreamer" /> Livestreamer<br> <br>
What's your motivation?<br />
<textarea name="motivation" cols="60" rows="6"></textarea><br><br>
Why should we pick you as content creator?<br />
<textarea name="whyshouldwe" cols="60" rows="6"></textarea><br><br>
Do you have some reference material?<br />
<textarea name="reference" cols="60" rows="6"></textarea><br><br>
<h3>Rules to content creation</h3>
<p>You can only submit this once every day, the other versions will not be read, and you will lose Karma for each submit.<br />
When u submit this form, we will examine your account, and we will take a close look to your reference material.<br>
<h4>For Livestreamers Only</h4>
If we think you have what it takes to be a livestreamer ( frequent hours required ) we will examine your stream, and your computer/internet potential.<br />
If that is good enough for the website, you'll become a content creator.<br>
<h4>For Bloggers</h4>
If we think you are blogging material for out website, you will become a content creator, once you are accepted onto the team we will track your progress.<br />
If however you neglect your power or publish inappropriate content, then we will have no choice but to remove you from our team and will revert you to a regular user account.<br><br>
<input name="Send" type="submit" id="art-button-wrapper" value="I donate 500 Karma, and want to become a 'Content Creator'!" />
</form>

PHP Handler DOC

<?php 
//get content out of form
$nick = $_REQUEST['username'];
$mail = $_REQUEST['mail'];
$cct = $_REQUEST['CCT'];
$motiv = $_REQUEST['motivation'];
$why = $_REQUEST['whyshouldwe'];
$ref = $_REQUEST['reference'];
$userID = $_REQUEST['UserID'];
$errors = '';

//database connection script
include "DBConnection.php";

//get connection
$con = getconnection();

//is connection available
if (!$con)
{
  die('Could not connect: ' . mysql_error());
}

//select database
mysql_select_db("brokendi_BD", $con);

//get current karma
$result = mysql_query("SELECT * FROM userpoints WHERE uid='$userID'");
$row = mysql_fetch_array($result);
$currentkarma = (int)$row['points'];


//check karma level
if ($currentkarma < 499)
{
        $errors .= "
 Error: Not enough karma";
}

//check nickname
if(empty($nick))
{
    $errors .= "
 Error: Username is required";
}

//check e-mail field
if(empty($mail))
{
    $errors .= "
 Error: E-mail is required";
}

//check cct field
if(empty($cct))
{
    $errors .= "
 Error: Content Creator Type is required";
}

//e-mail validation
if (!preg_match(
"/^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$/i", 
$mail))
{
    $errors .= "
 Error: Invalid email address";
}

//send e-mail and deduct karma
if( empty($errors))
{
        $newkarma = $currentkarma-500;
        mysql_query("UPDATE userpoints SET points = '$newkarma' WHERE uid='$userID'");

    $to = "support@brokendiamond.org"; 
    $email_subject = "$nick: I want to become a content creator";
    $email_body = " Nickname: $nick 
 Email: $mail
 Content Creator Type: $cct
 Motivation:
 $motiv

 Why should we accept you:
 $why

 reference:
 $ref"; 

    mail($to,$email_subject,$email_body,"From: $mail");
    mail($mail,"Content Creator application","Dear $nick,

Your application has been recieved and will be answered as soon as we can, usually this takes less than 24 hours,
but occasionaly this might take us longer.

Kind regards,
The Broken Diamond Team","From: no-reply@brokendiamond.org");
    header('Location: http://brokendiamond.org');
}

//close connection
mysql_close($con);
?>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 
<html>
<head>
    <title>Contact form handler</title>
</head>

<body>
<!-- This page is displayed only if there is some error -->
<?php
echo nl2br($errors);
?>


</body>
</html>

This is not proper way to code in Drupal. You can use inbuilt form set errors to display as you wanted. please go through some drupal tutorials for forms and may be module development as well. I thought this is PHP code until i noticed $user->uid :) For DB related APIs