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php连接数据库
/**************denglu.php****************/
session_start();
$username=$_POST['username'];
$password=$_POST['password'];
@ $db = mysql_connect('localhost','root','root'); //连接数据库
if (!$db) {
     die('Could not connect: ' . mysql_error());
}
//echo '连接成功!';
    mysql_select_db('wwj');     //选择数据库文件wwj
//执行SQL 语句
   mysql_query("set names utf8");//数据库中是utf8 ,没有“-”.网页中有!!
 $sql="select * from pre_common_member where username=$username";
 $res=mysql_query($sql);
 if($row=mysql_fetch_assoc($res)){
  if($row['password']==md5($password)){
  $name=$row['username'];
  echo"<script>alert('登陆成功!')</script>";
  session_register('$name');
  header('Location:ClassWeb.php');exit();
  }
  }
   echo"<script>alert('用户名或密码错误!')</script>";
  header('Location:ClassWeb.php');exit();
  mysql_free_result($res);
?>
我输入的账号的密码是对的,但是提示信息是乱码,我也不知道是登陆成功还是错误,提示窗口出现后,我点击确定,第二个警告错误才出现!!!!错误:
Warning: mysql_fetch_assoc(): supplied argument is not a valid MySQL result resource in F:\Apache HTTP Server\AppServ\www\ClassWeb\denglu.php on line 15

Warning: Cannot modify header information - headers already sent by (output started at F:\Apache HTTP Server\AppServ\www\ClassWeb\denglu.php:15) in F:\Apache HTTP Server\AppServ\www\ClassWeb\denglu.php on line 24
------解决思路----------------------
$sql="select * from pre_common_member where username='$username'";
------解决思路----------------------
弹窗乱码是因为你的程序文件不是 utf-8 的
错误信息是因为你在 
header('Location:ClassWeb.php'); 
前有输出
echo"<script>alert('用户名或密码错误!')</script>";
------解决思路----------------------
php连接数据库显示示例
//数据库连接conn.php页面
 $conn=mysql_connect("localhost","root","root"); //连接数据库服务器
 mysql_select_db("db_forumm",$conn); //连接指定的数据库
 mysql_query("set names gb2312"); //对数据库中的编码格式进行转换,避免出现中文乱码的问题
?>
//功能页面显示数据

$tb_forum_name=$_SESSION["tb_forum_name"];//记录用户名
if($tb_forum_name==""){
echo "<script>alert('您还没有登录!');window.location.href='index.php';</script>";//登录控制
exit;
}//codego.net/tags/4/1/
    $sql=mysql_query("select * from tb_forum_user where tb_forum_name='".$tb_forum_name."'",$conn);
    $info=mysql_fetch_array($sql);//选择数据库数据
?>




                                  
                                    
                                  
                                  
                                    
                     
                                  
                                  
                                    
                                    
                                  
    
                                    
                                    
                                  
                                  
                                    
                                    
                                  
                                  
                                    
                                    
                                  
  
                                    
                                    
                                  
   
                                                                      
                                  
                                  
                                    
  
 
会员名:
  
密码:
 
         " maxlength="12">
移动电话:
 
                                      " maxlength="11">
邮箱地址:
 
            " maxlength="16" />
                                       (请填写正确的E-mail地址!)
QQ号码:
 
            " maxlength="12" />
                                     (QQ号只能由数字组成!)
性别:
 
             " maxlength="2">
 
 " maxlength="16">

                                      
                                      

                                        php连接数据库,该如何解决
                                        
                                          
                                        
                                      
 
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