php, check if mail is valid - php

Question

I know that there is a ton of solutions to this problem but i need to validate email in a contact form.
this is my php mailer so far:
<?php
if (isset($_POST['send'])){
$to = "mail#mail.something";
$subject = "new message";
$firstname = $_POST['name'];
$email = $_POST['email'];
$message = $_POST['message'];
$headers = "From: $email";
$sent = mail($to, $subject, $message, $headers) ;
if($sent)
{echo "<script>alert('thanks for the message:) ');</script>";
}else
{echo "<script>alert('sorry, message wasn't send');</script>"; }
}
?>
I have tried with filter_var
$result = filter_var( 'something#something.something', FILTER_VALIDATE_EMAIL );
but, doesn't work.
If my way to sent mail through contact form isn't the "best practice way" feel free to correct me and send me on the right path :D

Answer 1

If you show us your HTML we can help further, but with just your PHP we don't have much to work with.
Add error_reporting(E_ALL); and ini_set('display_errors', 1); to the top of your php page to print your errors.
I am not sure what is causing your errors. But i would like you to try the following code. Replace your if statement with this.
Future note, to add a javascript alert in php you should format it this way,
if(mail($to, $subject, $message, $headers))
{
echo '<script language="javascript">'; //echo open tag
echo 'alert("Your message has been sent")'; // echo alert
echo '</script>'; //echo close tag
}else{
echo '<script language="javascript">';
echo 'alert("Your message was not successful")';
echo '</script>';
}