PHP Mail function didn't work - php

Question

I have use php contact form for my web site.but it's doesn't work properly.when i fill all the field correctly and submit. it's display error message "Invalid data" .
<?php
$action=$_REQUEST['action'];
if ($action=="")
{
?>
<form action="" method="POST" enctype="multipart/form-data">
<input type="hidden" name="action" value="submit">
Your name:<br>
<input name="name" type="text" value="" size="30" required/><br>
Your email:<br>
<input name="email" type="email" value="" size="30" required /><br>
Your message:<br>
<textarea name="message" rows="7" cols="30" required></textarea><br> <br>
<input type="submit" value="Send email" class="topbarbtn"/>
</form>
<?php
$subject=$_REQUEST['name'];
$email=$_REQUEST['email'];
$body=$_REQUEST['message'];
}else{
$to = "abc#abc.com";
$subject = $subject;
$from = $email;
$message = $body;
if (($from=="")||($subject=="")||($message==""))
{
echo '<script type="text/javascript">alert("Invalid Details");</script>' ;
} else{
$headers = "From: " . $from . "\r\n";
$body .= $message;
mail($to, $subject, $body, $headers);
}
?>

Answer 1

Like this it works:
<?php
$action=$_REQUEST['action'];
if ($action=="") {?>
<form action="" method="POST" enctype="multipart/form-data">
<input type="hidden" name="action" value="submit">
Your name:<br>
<input name="name" type="text" value="" size="30" required/><br>
Your email:<br>
<input name="email" type="email" value="" size="30" required /><br>
Your message:<br>
<textarea name="message" rows="7" cols="30" required></textarea><br> <br>
<input type="submit" value="Send email" class="topbarbtn"/>
</form>
<?php
}
else {
$to = "...mail address...";
$subject = $_REQUEST['name'];
$from = $_REQUEST['email'];
$message = $_REQUEST['message'];
if (($from=="")||($subject=="")||($message=="")) {
echo '<script type="text/javascript">alert("Invalid Details");</script>' ;
}
else{
$headers = "From: " . $from . "\r\n";
$body .= $message;
mail($to, $subject, $body, $headers);
}
}
?>

Answer 2

Noticed a flaw in your logics - you try to set $from as an $email, while you don't get a variable $email
in else statement add this lines:
$from = $_REQUEST['email'];
Plus if mail still is not sending you should considerthat some mail servers, such as qmail, will reject your message if it uses \r\n.
So you should try to use just \n or \n\n as a linebreak in a header.