请给这段PHP代码解密！ 多谢！

解密后的代码如下：

<?php
include 'config.php';
function ipn_debug_email($message,$email_address = '',$always_send = false,$subjecttext = 'IPN DEBUG message') {
static $paypal_instance_id;
if(OPEN_DEBUG) {
if(!isset($paypal_instance_id)) $paypal_instance_id = time() .'_'.rand(0,9).rand(0,9).rand(0,9).rand(0,9);
$paypal_error_counter ++;
ipn_add_error_log($message,$paypal_instance_id);
}
}
function ipn_add_error_log($message,$paypal_instance_id = '') {
if ($paypal_instance_id == '') $paypal_instance_id = date('mdYGi');
$fp = @fopen('logs/post_'.$paypal_instance_id .(substr($message,0,3) == 'PDT'?'_PDT': '') .'.log','a');
if ($fp) {
fwrite($fp,date('M d Y G:i') .' -- '.$message ."\n\n");
fclose($fp);
}
}
function ipn_postback($mode = 'IPN') {
$