stuck with php submit response - php

Question

I cant figure out whats wrong with the code.
The problem occurs when i try to send form data to email.
So far its good but i cant get response code to work.
I mean when i fill form and click send it wont show predefined error when some of the forms are empty or when it was sent. Response should be in a same window or form.
Code i have at the moment:
<form name="action" method="post" onsubmit="return false;">
<?php if( isset($error_msg) && $error_msg != '' ) { echo $error_msg; } ?>
<input type="text" name="name" id="name" placeholder="Ees-ja perekonnanimi">
<input type="text" name="cname" id="cname" placeholder="Ettevõtte nimi" style="width: 55%;"> <input type="text" name="regnum" id="regnum" placeholder="Reg. number" style="width: 25%;">
<input type="text" name="email" id="email" placeholder="E-post">
<textarea name="info" placeholder="Sõnum" cols="40"></textarea>
<input type="submit" value="Esita" onclick="return getData()">
<div id="error_msg"><?php echo $error_msg; ?></div>
<?php
if ($_SERVER["REQUEST_METHOD"] == "POST")
{
$action=$_REQUEST['action'];
{
$name=$_REQUEST['name'];
$cname=$_REQUEST['cname'];
$regnum=$_REQUEST['regnum'];
$email=$_REQUEST['email'];
$info=$_REQUEST['info'];
if (($name=="")||($email==""))
{
$error_msg="All fields are required";
}
else{
$data="Kliendi nimi: $name \r\nEttevõtte nimi: $cname \r\nEttevõtte reg. number: $regnum \r\nE-post: $email \r\nSõnum: $info";
$subject="Tellimus";
mail("someone#somewhere.com", $subject, $data);
$error_msg="Your message was sent, Thank you!";
}
}
}
?>
</form>
any advice?