Proxy Block proxy checker Script

<?php
/*
    --------------------
    Proxy Block Script
    --------------------

    Created by 1337 Brain
    Date    2011/07/08
    Version 1.0.4

    Requirements:
    = PHP 5.2 or higher
    = MySQL 5 or higher

    License: CC BY-SA 3.0
*/

function check_proxy()
{
    /*---------------------
     * Configuration start
     *--------------------*/

    // Database information
    $db_hostname  = 'localhost';
    $db_database  = 'proxydb';
    $db_username  = 'username';
    $db_password  = 'password';
    $db_installed = false; // change to true after executing 1st time

    // Ports to check
    $check_ports = true;
    $ports = array(3128,8080);

    // Proxy headers
    $check_headers = true;
    $headers = array('HTTP_VIA', 'HTTP_X_FORWARDED_FOR', 'HTTP_FORWARDED_FOR', 'HTTP_X_FORWARDED', 'HTTP_FORWARDED', 'HTTP_CLIENT_IP', 'HTTP_FORWARDED_FOR_IP', 'VIA', 'X_FORWARDED_FOR', 'FORWARDED_FOR', 'X_FORWARDED', 'FORWARDED', 'CLIENT_IP', 'FORWARDED_FOR_IP', 'HTTP_PROXY_CONNECTION');

    // Banned
    $banned_ips = array('193.200.150.');
    $banned_useragents = array();

    // Allowed
    $allowed_ips = array('127.0.0.');
    $allowed_useragents = array('Googlebot','msnbot','Slurp');

    // Notes:
    // You are able to ban/allow an IP range such as 1.0.0.0 -> 1.0.0.255
    // by banning/allowing the IP "1.0.0."

    /*---------------------
     * Configuration end
     *--------------------*/

    // Init
    error_reporting(0);
    ini_set("default_socket_timeout",1);
    $proxy     = false;
    $userip    = (string) $_SERVER['REMOTE_ADDR'];
    $useragent = (string) $_SERVER["HTTP_USER_AGENT"];

    // Fix configuration
    if(!$check_ports)
    {
        $ports = array();
    }
    if(!$check_headers)
    {
        $headers = array();
    }

    // Ban certain IPs
    if( count($banned_ips) )
    {
        foreach($banned_ips as $ip)
        {
            $test = strpos($userip,$ip);

            if($test !== false && $test == 0)
            {
                return true;
            }
        }
        unset($ip);
    }

    // Ban certain User-Agents
    if( count($banned_useragents) )
    {
        foreach($banned_useragents as $ua)
        {
            $test = strpos($useragent,$ua);

            if($test !== false)
            {
                return true;
            }
        }
        unset($ua);
    }

    // Allow certain IPs
    if( count($allowed_ips) )
    {
        foreach($allowed_ips as $ip)
        {
            $test = strpos($userip,$ip);

            if($test !== false && $test == 0)
            {
                return false;
            }
        }
        unset($ip);
    }

    // Allow certain User-Agents
    if( count($allowed_useragents) )
    {
        foreach($allowed_useragents as $ua)
        {
            $test = strpos($useragent,$ua);

            if($test !== false)
            {
                return false;
            }
        }
        unset($ua);
    }

    // Check for proxy
    if( count($ports) || count($headers) )
    {
        // Connect and select database
        $db_link = mysql_connect($db_hostname,$db_username,$db_password) or die(mysql_error());
        mysql_select_db($db_database) or die(mysql_error());

        $db_setup = "CREATE TABLE IF NOT EXISTS `users` ( `ip` varchar(40) CHARACTER SET latin1 NOT NULL, `proxy` tinyint(1) NOT NULL, `time` DATETIME NOT NULL, UNIQUE KEY `ip` (`ip`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1;";
        $db_query = sprintf( "SELECT * FROM `users` WHERE `ip`='%s'",mysql_real_escape_string($userip) );

        // To select records created in the last 30 minutes
        $db_query .= " AND `time` > DATE_SUB( NOW(), INTERVAL 30 MINUTE)";

        // Has database been initialized?
        if( !$db_installed )
        {
            mysql_query($db_setup) or die(mysql_error());
        }

        // Now query for the IP address
        $db_result = mysql_query($db_query) or die(mysql_error());

        // Have we found it?
        while ($row = mysql_fetch_assoc($db_result))
        {
            // No need for a port scan or check for headers here
            return $row['proxy'];
        }

        // Check for proxy headers
        if( count($headers) )
        {
            foreach ($headers as $header)
            {
                if( isset($_SERVER[$header]) )
                {
                    $proxy = true;
                    break;
                }
            }
        }

        // Do a port scan
        if( !$proxy && count($ports) )
        {
            foreach($ports as $port)
            {
                $test = fsockopen($userip,$port);

                if($test !== false)
                {
                    fclose($test);
                    $proxy = true;
                    break;
                }
            }
        }

        // Delete older result and insert new
        $proxy = intval($proxy);
        $db_delete_ip = sprintf( "DELETE FROM `users` WHERE `ip`='%s'",mysql_real_escape_string($userip) );
        $db_insert_ip = sprintf( "INSERT INTO `users` VALUES ('%s','{$proxy}',NOW())",mysql_real_escape_string($userip) );
        mysql_query($db_delete_ip) or die(mysql_error());
        mysql_query($db_insert_ip) or die(mysql_error());
    }

    // Return result
    return $proxy;
}

if( check_proxy() )
{
    die("<title>403: Forbidden</title>Oops... A proxy");
}
?>