Register script with 1 ip limit?

[djfisring]

How can i get this script to check for ip as well?
1 account per ip like the username.

<?php
            if(isset($_POST["go"])){
                foreach ($_POST as $key => $protect) {
                    $_POST[$key] = addslashes($protect);
                }
                $user     = $_POST["user"];
                $password = $_POST["password"];
                $password1= $_POST["password1"];
                $email    = $_POST["email"];
                $email1   = $_POST["email1"];
                $name     = $_POST["name"];
                $sex      = $_POST["sex"];
                $code     = $_POST["code"];
                if(!$user) {
                    $error[]="Please fill username input.";
                } else {
                    if(strlen($user) < 6)   $error[] = "Username too short.";
                    if(strlen($user) > 16)  $error[] = "Username too long.";
                    if(!ctype_alnum($user)) $error[] = "Username should be Characters and Numbers only.";
                }
                
                if(!$password) {
                    $error[]= "Please fill password input";
                } else {
                    if(strlen($password) < 6)   $error[] = "Password too short.";
                    if(strlen($password) > 32)  $error[] = "Password too long.";
                    if(!ctype_alnum($password)) $error[] = "Password should be Characters and Numbers only.";
                }
                
                if(!$password1) {
                    $error[]="Please fill confirm password input.";
                } else {
                    if(strlen($password1) < 6)  $error[] = "Confirm Password too short.";
                    if(strlen($password1) > 32) $error[] = "Confirm Password too long.";
                }
                
                if ($password && $password1) {
                    if($password !== $password1){$error[] = "Passwords are not the same";}
                }
                
                if(!$email) {
                    $error[]="Please fill E-mail input";
                }
                if(!$email1) {
                    $error[]="Please fill confirm  E-mail input";
                }
                if ($email && $email1) {
                    if(!filter_var($email, FILTER_VALIDATE_EMAIL)) $error[]= "E-mail is not valid";
                    if($email !== $email1){$error[] = "E-mails are not the same";}
                }
                if(!$name) {
                    $error[]="Please fill name input";
                } else {
                    if(!ctype_alnum($name)) $error[] = "Name should be Characters and Numbers only";
                }
                if(!$sex) {
                    $error[]="Please choose sex";
                } else {
                    if(!ctype_alnum($sex)) $error[] = "Sex should be Characters and Numbers only";
                    if ($sex > 2 || $sex < 0) {
                        $error[] = "There some thing wrong with sex!";
                    } else {
                        if ($sex == 1) {
                            $sex = "M";
                        } else if ($sex == 2) {
                            $sex = "F";
                        }
                    }
                }
                if(!$code) {
                    $error[]="Please fill code input";
                } else {
                    if($code != $_SESSION["captcha"]){$error[]= "Wrong captcha Code !";}
                }
                
                $check = odbc_exec($connect, "SELECT * FROM TB_User WHERE StrUserID = '".$user."'");
                if (odbc_num_rows($check) > 0) {
                    $error[] = "Account with such username already exists please chose another one";
                }
                
                if (@count($error) > 0) {
                    echo "
                    <div id=\"boxes\">
                        <div id=\"dialog\" class=\"window\">
                            <b style=\"float:left;\">Message</b><div title=\"close\" id=\"close\">X</div><br /><hr />
                            <div class=\"content\">
                                <ol>
                    ";
                    for($e=0;$e<count($error);$e++) {
                        echo "
                            <li>".$error[$e]."</li>
                        ";
                    }
                    echo "
                                    </ol>
                                </div>
                            </div>
                            <div id=\"mask\"></div>
                        </div>
                        <script type=\"text/javascript\">
                            dialog();
                        </script>
                    ";
                } else {
                    @$register = odbc_exec($connect, "INSERT INTO TB_User(StrUserID, password, Name, Email, sex, reg_ip, sec_primary, sec_content) VALUES ('".$user."', '".md5($password)."', '".$name."', '".$email."', '".$sex."', '".$ip."', '3', '3')");
                    if ($register) {
                        
                        $find = odbc_fetch_array(odbc_exec($connect, "SELECT * FROM TB_User WHERE StrUserID = '".$user."'"));
                        $gift = $find["JID"];
                        odbc_exec($connect, "INSERT INTO SK_Silk(JID, silk_own) VALUES (".$gift.", ".$silk.")");
                        odbc_exec($connect, "USE SRO_VT_SHARD INSERT INTO _AccountJID(AccountID, JID, Gold) VALUES ('".$user."',".$gift.", ".$gold.")");
                        echo "
                            <script type=\"text/javascript\">
                                alert(\"Register complete\");
                            </script>
                        ";
                        
                        if ($home != "") {
                            echo "
                                <script type=\"text/javascript\">
                                    window.location = \"".$home."\";
                                </script>
                            ";
                        }
                        
                    } else {
                        echo odbc_errormsg();
                    }
                }
            
            }
        ?>

[MentaL]

[IMOS]

$check = odbc_exec($connect, "SELECT * FROM TB_User WHERE reg_ip = '".$ip."'"); 
                if (odbc_num_rows($check) > 0) { 
                    $error[] = "Only one account per IP allowed."; 
                } 

$ip = getenv("REMOTE_ADDR") ; 

[FuriousRage]

How would I make a script or change this one to allow more than 1 IP for e.g. 2-3?