// Change 'email' to the name of the field where your user should 
// enter their own email address.
if (empty($_POST) || !isset($_POST['email'])) {
    header("Location: /");
    exit;
}

// Your form should have a honey pot field 'pooh' that is left blank by human users
if (!isset($_POST['pooh']) || $_POST['pooh']!="") {
    sleep(rand(2, 5)); // delay spammers a bit
    header("HTTP/1.0 403 Forbidden");
    exit;
}
$crlf = "\r\n";

// Insert into PHP scripts before mail()

// Check $_GET if your contact form uses GET method.

$badStrings = array("Content-Type:",
"MIME-Version:",
"content-type:",
"mime-version:",
"multipart/mixed",
"content-transfer-encoding:",
"to:",
"Content-Transfer-Encoding:",
"bcc:",
"cc:",
"href=");

function all_ascii( $stringIn ){
    $final = '';
    $search = array("\r","\n");
    $replace = array(" "," ");
    
    $hold = str_replace($search[0],$replace[0],$stringIn);
    $hold = str_replace($search[1],$replace[1],$hold);
    
    if(!function_exists('str_split')){
        function str_split($string,$split_length=1){
            $count = strlen($string);
            if($split_length < 1){
                return false;
                } elseif($split_length &gt; $count){
                return array($string);
                } else {
                $num = (int)ceil($count/$split_length);
                $ret = array();
                for($i=0;$i < $num;$i++){
                    $ret[] = substr($string,$i*$split_length,$split_length);
                }
                return $ret;
            }
        }
    }
    $holdarr = str_split($hold);
    foreach ($holdarr as $val) {
        if (ord($val) < 128) $final .= $val;
    }
    return $final;
}
// Loop through each POST'ed value and test if it contains
// one of the $badStrings:
foreach($_POST as $k =&gt; $v){
    foreach($badStrings as $v2){
        if(strpos(all_ascii($v), $v2) !== false){
            sleep(rand(2, 5)); // delay spammers a bit
            header("HTTP/1.0 403 Forbidden");
            exit;
        }
    }
}
// Continue onward to mail()