$_POST doesnt work - php

Question

I have a simple contact me script, which fires an email on submit.
The email is sent, but there are no form values in the email (name: empty, ...).
Why doesn't my contact script work?
<?php
if ($action == "send") //isset wyslij
{
if (!$_POST[name] || !$_POST[email] || !$_POST[phone] || !$_POST[enquiry])
{
$problem = TRUE;
echo("<p>You have to fill all form.</p>");
}
if (! $problem)
{
$data = date("d.m.y");
$message = "
<p>Name: $_POST[name]</p>
<p>Phone: $_POST[phone]</p>
<p>Email: $_POST[email]</p>
<br>
<p>Enquiry: $_POST[enquiry]</p>";
$od = "contactmail#asdasdas.com";
$content = $message;
$header = "From: $od \r\n";
$header .= 'MIME-Version: 1.0' . "\r\n";
$header .= 'Content-type: text/html; charset=UTF-8' . "\r\n";
(mail('email#example.com', 'New message from website', $content, $header));
echo("<br><p>Message has been sent.</p>");
}
else
{
echo("<p>Try <a href=contact.php>again</a></p>");
}
}
?>
<form action="contact.php?action=send" method="post" enctype="text/plain">
<label for="name">Name</label><input type="text" name="name" /></br></br>
<label for="email">Email</label><input type="text" name="email" /></br></br>
<label for="phone">Phone</label><input type="text" name="phone" /></br></br>
<label for="enquiry">Enquiry</label><textarea name="enquiry" cols="20" rows="10"></textarea></br></br>
<input type="submit" id="contact_button" value="Send" />
</form>

Answer 1

Valid values for enctype in tag are:
application/x-www-form-urlencoded
multipart/form-data
you have text/plain and thats why it's not working.

Answer 2

simply remove the "enctype" argument from the HTML form code and try again?