如何连接数据库服务器

<?php
 header('Content-Type:text/html;charset=utf-8');
 define('DB_HOST','localhost');
 define('DB_USER','root'); 
 define('DB_PASS','root');
  define('DB_CHAR','utf8'); 
  $db=@mysql_connect(DB_HOST,DB_USER,DB_PASS); 
  if(!$db){  
       echo die('Could not connect'.mysql_error()); 
     }else{ 
         mysql_select_db('demo');    
         $sql='SELECT * FROM user';    
         $res=mysql_query($sql,$db);   
         $num=mysql_num_rows($res);    
         var_dump($num);    
         echo '<table border="1" cellpadding="0" cellspacing="0" width="800">';  
           echo '<tr>';    
           echo '<th>ID</th>';    
           echo '<th>name</th>';    
           echo '<th>password</th>';  
           echo '<th>email</th>';   
            echo '<th>mobbile</th>';    
            echo '<th>img</th>';    
            echo '</tr>';    
            while($res1=mysql_fetch_assoc($res)){     
            echo '<tr>';     
            echo  '<td>'.$res1["id"].'</td>';    
            echo  '<td>'.$res1["name"].'</td>';    
             echo '<td>'.$res1["password"].'</td>';     
             echo '<td>'.$res1["email"].'</td>';     
             echo '<td>'.$res1["mobbile"].'</td>';    
              echo '<td><img src='.$res1["img"].' width="60"></td>';    
               echo '</tr>';   
                }    
                echo '</table>'; 
                }
 ?>