函数getip（）需要更新才能更安全和准确

Need suggestions to update following function for detection of IP address to be more accurately and safer from SQL injection via user input

function getip(){
if(!empty($_SERVER['HTTP_CLIENT_IP'])){
  $ip=$_SERVER['HTTP_CLIENT_IP'];
}else if(!empty($_SERVER['HTTP_X_FORWARDED_FOR'])){
  $ip=$_SERVER['HTTP_X_FORWARDED_FOR'];
}else{
  $ip=$_SERVER['REMOTE_ADDR'];
}
$ip = strtolower($ip);
 if(substr_count($ip,"unkown")>0){
 $ip=$_SERVER['REMOTE_ADDR'];
}
$ip = htmlspecialchars($ip);
$ip = mysql_real_escape_string($ip); 
return $ip;    

Run this edit OnLine

function getip() 
{ 
$keyname_ip_arr = array('HTTP_X_FORWARDED_FOR', 'HTTP_REMOTE_ADDR_REAL', 'HTTP_CLIENT_IP', 'HTTP_X_REAL_IP', 'REMOTE_ADDR'); 
foreach ($keyname_ip_arr as $keyname_ip) { 
if (!empty($_SERVER[$keyname_ip])) { 
$ip = $_SERVER[$keyname_ip]; 
 if (strstr($ip, ',')) { 
 $ips = explode(',', $ip); 
 foreach ($ips as $ip) 
{ 
if(filter_var(trim($ip), FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE)) break(2); 
} 
} 
elseif(filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE)) break; 
} 
} 
return $ip; 
list($ip1,$ip2,$ip3,$ip4) = explode('.',$ip); 
return $ip1.'.'.$ip2.'.'.$ip3.'.0'; 
}