PHP cc attack defense and fast refresh code

//Exit the proxy IP directly
empty($_SERVER['HTTP_VIA']) or exit('Access Denied');
//Prevent quick refresh
session_start();
$seconds = '3'; //Time period [seconds]
$refresh = '5'; //Number of refreshes
//Set monitoring variables
$cur_time = time();
if(isset($_SESSION['last_time'] )){
 $_SESSION['refresh_times'] += 1;
}else{
 $_SESSION['refresh_times'] = 1;
 $_SESSION['last_time'] = $cur_time;
}
//Process monitoring results
if($cur_time - $_SESSION['last_time'] < $seconds){
 if($_SESSION['refresh_times'] >= $refresh){
 //Jump to attacker server address
 header(sprintf ('Location:%s', 'http://127.0.0.1'));
 exit('Access Denied');
 }
}else{
 $_SESSION['refresh_times'] = 0;
 $_SESSION[ 'last_time'] = $cur_time;
}
?>