php 用户注册实例代码，适合初学者_PHP教程

php教程 用户注册实例代码，适合初学者
  if($_POST[submit]){

   checkusername($_POST[username]);

    if($_SESSION["code"]==$_POST[code])

      {

    $username= str_replace(" ","",$_POST[username]);
    $password=md5($_POST[password].ALL_PS);
    $sql="INSERT INTO `member`.`user_list` (`uid`, `m_id`, `username`, `password`) VALUES (NULL, '$_POST[select]', '$username','$password' )";
    mysql教程_query($sql);
    echo "注册成功";
     }

    else
     {
      echo "验证码错误"."
";
      session_destroy();
     }
 }

   function checkusername($username)
          {
           $sql2 = "select uid from user_list where username='".mysql_escape_string($username)."'";
            $result = mysql_query($sql2) or die ('ERROR: '.mysql_error());
            if(mysql_num_rows($result)>0)
                {
                echo "该用户名已经存在，请更换！";

                exit();
                 }
            else{
                 echo "<script> location.href='reg.php'</script>";
                 }

           }

?>