How to get PHP to work in WordPress Posts?

How to get this working in the Post HTML? :

<?php
// declare values
$contact_email = $_POST[‘EmailAddress’];
$contact_subject = $_POST[‘Subject’];
$contact_name = $_POST[‘FullName’];
$contact_message = $_POST[‘Message’];
$mydate = date ( ‘l, F d Y g:i A’,time()+240 );

// where to send e-mail to
$to = ‘[email protected]’;

// e-mail subject
$subject = “Message submitted from iHolyElement”;

// e-mail message
$message = “You have received a contact message:\r\n”

.”—————————————————————-\r\n”
.”Contact Name: $contact_name\r\n”
.”Subject: $contact_subject\r\n”
.”Submitted: $mydate\r\n”
.”From IP: {$_SERVER[‘REMOTE_ADDR’]}\r\n\r\n”
.”Message: $contact_message\r\n”
.”Form Address: {$_SERVER[‘SERVER_NAME’]}{$_SERVER[‘REQUEST_URI’]}”;

$headers = “From: $contact_name <$contact_email>\n”
.”Reply-To: $contact_email\n”
.”X-Mailer: PHP/”.phpversion();

// check for validation, then send the e-mail
if(empty($contact_name) || empty($contact_email) || empty($contact_subject) || empty($contact_message)) {
echo ‘<p>Send us a message, enter your information below and click \’Submit\’!</p>
<form method=”post” action=””>
<table id=”Form-Details”>
<tbody>
<tr><td>Name:</td><td><input type=”text” name=”FullName” size=”20″ /></td>
<td>Subject:</td><td><input type=”text” name=”Subject” size=”20″ /></td></tr>
<tr><td>Email:</td><td colspan=”3″><input type=”text” name=”EmailAddress” size=”20″ /></td></tr>
<tr><td colspan=”4″>Message:</td></tr>
<tr><td colspan=”4″><textarea rows=”6″ name=”Message” cols=”47″ class=”input”></textarea></td></tr>
<tr><td colspan=”4″ class=”right1″><input type=”submit” value=”Submit” /><input type=”reset” value=”Reset” /></td></tr>
</tbody>
</table>
</form>’;
} elseif(!ereg(“^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$”, $contact_email)) {
echo “<p>ERROR: Please enter a valid e-mail address.</p>”;
} else {
mail( $to, $subject, $message, $headers );
echo “<h3>Message Sent!</h3><p>Dear $contact_name,

We will get back to you as soon as possible using $contact_email.”;
}
?>