Retrieve values from HTML form

I have a mail sending functionality in php code, I want to use define to set to address and from address.How can this be done.

The code is

   <?php

 $subject = 'Test email';

$message = "Hello World!\n\nThis is my first mail.";

$headers = "From: $from\r\nReply-To: webmaster@example.com";
  //send the email
   $mail = @mai开发者_运维技巧l( $to, $subject, $message, $headers );

 ?>

How to define $to and $from. Thanks in Advance for help

Unless it is absolutely imperative, I would recommend using a good old fashioned variable for this particular task, not a constant.

If you do want to use a constant:

define('MAIL_TO', 'mailto@gmail.com');
define('MAIL_FROM', 'mailfrom@gmail.com');

$subject = 'Test email';
$message = "Hello World!\n\nThis is my first mail.";
$headers = "From: " . MAIL_FROM . "\r\nReply-To: webmaster@example.com";

$mailResult = mail(MAIL_TO, $subject, $message, $headers);

FYI:

// Constants can also be retrieved with the constant() function
$mailTo = constant('MAIL_TO');

// ...which is the same as...
$mailTo = MAIL_TO;

With use of constants:

$mailTo   = 'mailto@gmail.com';
$mailFrom = 'mailfrom@gmail.com';
$subject  = 'Test email';
$message  = "Hello World!\n\nThis is my first mail.";
$headers  = "From: " . $mailFrom . "\r\nReply-To: webmaster@example.com";

$mailResult = mail($mailTo, $subject, $message, $headers);

Here's a very basic example. I'll leave it up to you to do validation.

HTML:

<form action="path/to/your/script.php" method="post">
  <input type="text" name="from" />
  <input type="submit" value="Send" />
</form>

PHP:

In PHP, you'll want to use $_REQUEST, $_POST or $_GET depending on the action parameter of the form in your HTML. If you're not sure, use $_REQUEST. The value that goes in the square brackets is the name of attribute of the input from your HTML.

define('TO_ADDRESS', 'user@example.org');

$headers = "From: " . $_REQUEST['from'] . "\r\nReply-To: webmaster@example.com";
$mail = mail(TO_ADDRESS, $subject, $message, $headers);