A webpage to check an IP against the blacklist servers\\
<code>
<html>
    <head>
        <title>DNSBL Lookup Tool - IP Blacklist Check Script</title>
    </head>
    <body>
        <form action="" method="get">
            <input type="text" value="" name="ip" />
            <input type="submit" value="LOOKUP" />
        </form>
         <?php 
        /*************************************************************************************** 
        This is a simple PHP script to lookup for blacklisted IP against multiple DNSBLs at once. 

        You are free to use the script, modify it, and/or redistribute the files as you wish. 

        Homepage: http://dnsbllookup.com 
        ****************************************************************************************/ 
        function dnsbllookup($ip){ 
            $dnsbl_lookup=array("dnsbl-1.uceprotect.net","dnsbl-2.uceprotect.net","dnsbl-3.uceprotect.net","dnsbl.dronebl.org","dnsbl.sorbs.net","zen.spamhaus.org"); // Add your preferred list of DNSBL's 
            if($ip){ 
                $reverse_ip = implode(".", array_reverse(explode(".", $ip))); 
                foreach($dnsbl_lookup as $host){ 
                    if(checkdnsrr($reverse_ip.".".$host.".", "A")){ 
                        $listed .= $reverse_ip.'.'.$host.' <font color="red">Listed</font><br />'; 
                    } 
                } 
            } 
            if($listed){ 
                return $listed; 
            }else{ 
                return '"A" record was not found'; 
            } 
        } 
        $ip=$_GET['ip']; 
        if(isset($_GET['ip']) && $_GET['ip']!=null){ 
            if(filter_var($ip,FILTER_VALIDATE_IP)){ 
                echo dnsbllookup($ip); 
            }else{ 
                echo "Please enter a valid IP"; 
            } 
        } 
        ?> 
    </body>
</html>
</code>