<?php
	/*
	 * This is a PayPal IPN (Instant Payment Notification) broadcaster
	 * Since PayPal does not provide any straightforward way to add
	 * multiple IPN listeners we'll have to create a central IPN
	 * listener that will broadcast (or filter and dispatch) Instant
	 * Payment Notifications to different destinations (IPN listeners)
	 *
	 * Destination IPN listeners must not panic and recognize IPNs sent
	 * by this central broadcast as valid ones in terms of source IP
	 * and any other fingerprints. Any IP filtering must add this host,
	 * other adjustments made as necessary.
	 *
	 * IPNs are logged into files for debugging and maintenance purposes
     *
     * this code comes with absolutely no warranty
	 * http://codeseekah.com
	*/

	ini_set( 'max_execution_time', 0 ); /* Do not abort with timeouts */
	ini_set( 'display_errors', 'Off' ); /* Do not display any errors to anyone */
	$urls = array(); /* The broadcast session queue */

	/* List of IPN listener points */
	$ipns = array(
			'mystore' => 'http://mystore.com/ipn.php',
			'myotherstore' => 'http://mybigstore.com/paypal_ipn.php',
			'myotherandbetterstore' => 'http://slickstore.com/paypal/ipn.php'
		);
		
	/* Fingerprints */

	if ( /* My Store IPN Fingerprint */
		preg_match( '#^\d+\|[a-f0-9]{32}$#', $_POST['custom'] ) /* Custom hash */
		and $_POST['num_cart_items'] == 2 /* alwayst 1 item in cart */
		and strpos( $_POST['item_name1'], 'MySite.com Product' ) == 0 /* First item name */
	) $urls []= $ipns['mystore']; /* Choose this IPN URL if all conditions have been met */

	if ( /* My Other Store IPN Fingerprint */
		sizeof( explode('_', $_POST['custom']) ) == 7 /* has 7 custom pieces */
	) $urls []= $ipns['myotherstore']; /* Choose this IPN URL if all conditions have been met */

	/* My Other And Better Store IPN Fingerprint */
	$custom = explode('|', $_POST['custom']);
	if (
		isset($custom[2]) and $custom[2] == 'FROM_OB_STORE' /* custom prefixes */
	) $urls []= $ipns['myotherandbetterstore']; /* Choose this IPN URL if all conditions have been met */

	/* ... */
	
	
	/* Broadcast */
	
	if ( !sizeof($urls) ) $urls = $ipns; /* No URLs have been matched */
	$urls = array_unique( $urls ); /* Unique, just in case */

	/* Broadcast (excluding IPNs from the list according to filter is possible */
	foreach ( $urls as $url ) broadcast( $url );

	header( 'HTTP/1.1 200 OK', true, 200 );
	exit(); /* Thank you, bye */

	/* Perform a simple cURL-powered proxy request to broadcast */
	function broadcast( $url ) {

		/* Format POST data accordingly */
		$data = array();
		foreach ($_POST as $key => $value) $data []= urlencode($key).'='.urlencode($value);
		$data = implode('&', $data);

		/* Log the broadcast */
		file_put_contents('_logs/'.time().'.'.reverse_lookup( $url ).'-'.rand(1,100), $data);

		$ch = curl_init(); /* Initialize */

		curl_setopt($ch, CURLOPT_URL, $url);
		curl_setopt($ch, CURLOPT_POST, count($data));
		curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
		curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

		curl_exec($ch); /* Execute HTTP request */

		curl_close($ch); /* Close */
	}

	function reverse_lookup( $url ) {
		global $ipns;
		foreach ( $ipns as $tag => $_url ) {
			if ( $url == $_url ) return $tag;
		}
		return 'unknown';
	}
?>