mysql_real_escape_string在其他服务器上不起作用

我正在尝试在我的代码中使用mysql_real_escape_string。它适用于本地主机。而它在其他服务器上显示错误。我怎样才能找到解决方案。任何人都可以给我解决方案我的代码有什么问题吗

<?php
$username = "abcdb";
$password = "Abc@2014";
$hostname = "abcdb.db.9135182.hostedresource.com"; 
$db = "abcdb";
 $dbhandle = mysql_connect($hostname, $username, $password) or die("Unable to connect to MySQL");
mysql_select_db($db,$dbhandle) or die('cannot select db');
//connection to the database
$name="";
$email="";
$batch="";
$mobile="";
    if (isset($_POST['submit'])) {
    $error = "";

    if (!empty($_POST['name'])) {
   $name = mysql_real_escape_string($_POST['name']);
    } else {
    $error .= "You didn't type in your name. <br />";
    }
    if (!empty($_POST['email'])) {
    $email =mysql_real_escape_string($_POST['email']);
      if (!preg_match("/^[_a-z0-9]+('.[_a-z0-9-]+)*@[a-z0-9-]+('.[a-z0-9-]+)*('.[a-z]{2,3})$/i", $email)){ 
      $error .= "The e-mail address you entered is not valid. <br/>";
      }
    } else {
    $error .= "You didn't type in an e-mail address. <br />";
    }
if (!empty($_POST['batch'])) {
     $batch =mysql_real_escape_string($_POST['batch']);
if (!preg_match('/^[0-9]{4}$/', $batch))  { 
      $error .= "Enter a valid batch. <br/>";
      }
    }
    else {
    $error .= "You didn't type batch. <br />";
    }
     if(($_POST['code']) == $_SESSION['code']) { 
    $code = $_POST['code'];
    } else { 
    $error .= "The captcha code you entered does not match. Please try again. <br />";    
    }

    if (!empty($_POST['mobile'])) {
     $mobile =mysql_real_escape_string($_POST['mobile']);
    if (!preg_match('/^[0-9]{10}$/', $mobile)) { 
      $error .= "Enter a valid Mobile number. <br/>";
      }
    }else {
    $error .= "You didn't type your Mobile Number. <br />";
    }