Adding SIM (Server Integration Method) from Auth.net to WordPress

I need some help. We are starting to sell our products online, and so we are going to use the Auth.net implementation to do so. I’ve been able to set up the SDK, and configure the API’s on my server at elioverbey.net/sim.php // It works great!

The problem – I cannot get it to work on WordPress.

I need to get this php on a WordPress Page, but I cannot get it to run (because WordPress sees the PHP as text. Thoughts?

<?php
require_once 'anet_php_sdk/AuthorizeNet.php'; // Include the SDK you downloaded in Step 2
$api_login_id = '########';
$transaction_key = '#############';
$amount = "599.00";
$fp_timestamp = time();
$fp_sequence = "1" . time(); // Enter an invoice or other unique number.
$fingerprint = AuthorizeNetSIM_Form::getFingerprint($api_login_id,
  $transaction_key, $amount, $fp_sequence, $fp_timestamp)
?>

<form method='post' action="https://test.authorize.net/gateway/transact.dll">
<input type='hidden' name="x_login" value="<?php echo $api_login_id?>" />
<input type='hidden' name="x_fp_hash" value="<?php echo $fingerprint?>" />
<input type='hidden' name="x_amount" value="<?php echo $amount?>" />
<input type='hidden' name="x_fp_timestamp" value="<?php echo $fp_timestamp?>" />
<input type='hidden' name="x_fp_sequence" value="<?php echo $fp_sequence?>" />
<input type='hidden' name="x_version" value="3.1">
<input type='hidden' name="x_show_form" value="payment_form">
<input type='hidden' name="x_test_request" value="false" />
<input type='hidden' name="x_recurring_billing" value="no" />
<INPUT TYPE=HIDDEN NAME="x_description" VALUE="Product or order 
description.">
<input type='hidden' name="x_method" value="cc">
<INPUT TYPE=HIDDEN NAME="x_receipt_link_method" VALUE="LINK">
<INPUT TYPE=HIDDEN NAME="x_receipt_link_text" VALUE="Click here to return 
back to Medical Credentialing and Download the Master Survey">
<INPUT TYPE=HIDDEN NAME="x_receipt_link_URL" VALUE="http://
www.thriveworks.com">
<input type='submit' value="Click here for the secure payment form">
</form>