如何从数据库类调用连接到mysqli_real_escape_string()

这是我的数据库连接类。如何将连接链接调用到 mysqli_real_escape_string() 中。我收到一个错误，必须向 mysqli 函数提供另一个参数。我试着给 $this->link 但它不接受。

DBclass.php
class Database {

var $server   = "localhost"; //database server

var $user     = "root"; //database login name

var $pass     = ""; //database login password

var $database = "database name"; //database name

#######################

//internal info

var $error = "";

var $errno = 0;

//number of rows affected by SQL query

var $affected_rows = 0;
var $link_id = 0;

var $query_id = 0;





#-#############################################

# desc: constructor

function Database($server, $user, $pass, $database, $pre=''){

    $this->server=$server;

    $this->user=$user;

    $this->pass=$pass;

    $this->database=$database;

    $this->pre=$pre;



$this->link_id = mysqli_connect("$server", "$user", "$pass", "$database") or die("Could not connect : " . mysqli_error());

       mysqli_select_db($this->link_id,"$database") or die("Could not select database <b>$database</b>");











}#-#constructor()




And here is my registration page. I need to know how to give connection parameter to mysqli_real_escape_string (). Its showing error as mysqli_real_escape_string() needs one more parameter. Plese help out.. Thanks in advance

注册.php

if(isset($_POST['submit']))
{

  extract($_POST);


 $employee_id    =   mysqli_real_escape_string(htmlspecialchars(trim($employee_id)));
 $salutation     =   mysqli_real_escape_string(htmlspecialchars(trim($salutation)));
 $middle_name    =   mysqli_real_escape_string(htmlspecialchars(trim($middle_name)));
 $first_name     =   mysqli_real_escape_string(htmlspecialchars(trim($first_name)));
 $last_name  =   mysqli_real_escape_string(htmlspecialchars(trim($last_name)));  
 $gender     =   mysqli_real_escape_string(htmlspecialchars(trim($gender)));
 $dob        =   mysqli_real_escape_string(htmlspecialchars(trim($dob)));
 $mobile     =   mysqli_real_escape_string(htmlspecialchars(trim($mobile)));