YA: One Page Contact Form

<?php
/* Paste in response to yahoo answers question */

$output = ''; // Will hold the HTML to display to the user, based on the request scenario.
$HTML = Array( // $HTML Array to hold all the neccessary HTML
    'form' => // The Form HTML
        '<form method="post">
            <p>Your name</p>
            <p>
                <input type="text" name="cf_name">
            </p>
            <p>Your e-mail</p>
            <p>
                <input type="text" name="cf_email">
            </p>
            <p>Subject</p>
            <p>
                <input type="text" name="cf_subject">
            </p>
            <p>Message</p>
            <p>
                <input type="text" name="cf_message">
            </p>
            <p>Who do you want to contact:</p>
            <p>
                <select name="cf_address" size="1">
                    <option></option>
                    <option disabled>--Group--</option>
                    <option value="email">  Option</option>
                    <option value="email">  Option</option>
                    <option disabled>--Group--</option>
                    <option value="email">  Option</option>
                    <option disabled>--Group--</option>
                    <option value="email">  Option</option>
                    <option value="email">  Option</option>
                </select>
            </p>

            <input type="submit"value="Submit">
            <input type="reset" value="Clear">
        </form>
    ',
    'success' => // The HTML for the success message
        '<h3>Thank You</h3>
        <p>Your message has been received. <br> We thank you for taking the time to message us.</p>
        <p>Someone will respond to your message as soon as possible.</p>
    ',
    'error' => // Then HTML message for an error occuring
        '<h3>Internal Error</h3>
        <p>We\'re sorry to report that there has been an internal server error.</p>
        <p>Your message was not received. Please try again later.</p>
        <p>Sorry for any incovenience this has caused.</p>
    ');

if( $_SERVER['REQUEST_METHOD'] === 'POST' ){ // If the page is requested using the 'POST' method, the way in which your form requests the results page.
    // You should have a function to check the inputs for "Email Injections". Google it!
    // You should also be checking to see if any of the important fields are left blank.
    $field_name = $_POST['cf_name'];
    $field_email = $_POST['cf_email'];
    $subject = $_POST['cf_subject'];
    $field_message = $_POST['cf_message'];
    $mail_to = $_POST['cf_address'];

    $body_message = 'From: '.$field_name."\n";
    $body_message .= 'E-mail: '.$field_email."\n";
    $body_message .= 'Message: '.$field_message;

    $headers = 'From: '.$cf_email."\r\n";
    $headers .= 'Reply-To: '.$cf_email."\r\n";

    $mail_status = mail($mail_to, $subject, $body_message, $headers);

    if ($mail_status) {
        $output = $HTML['success'];
    } else {
        $output = $HTML['error'];
    }
}else{ // The request is a GET request
    $output = $HTML['form'];
}

echo $output;


?>