php+mysql实现超原始的注册登录

涉及主要知识点：
1.php操作mysql
2.加密函数md5()
3.php用？页面间传递参数
4.$_GET[]和$_POST[]
平台：redhat6+php5.3+mysql14.14+ Apache/2.2.15 (经典LAMP)
注册页面（regtest.php）：

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>welcome to regtest.php</title>
</head>
<body>
<h1>reg</h1>
<form method="post" action="reg_check.php">
  username<input type="text" name="username" >
  password:<input type="password" name="password">
  password again：<input type="password" name="pwd_again">
  <input type="submit" value="submit">
  <input type="reset" value="clean">
</form>
</body>
</html>

注册验证页面（reg_check.php）:
用于验证注册和写入数据库

<?php
  $db = mysql_connect("127.0.0.1","root","root") or die("Fail to connect db");
  mysql_select_db("userdb",$db) or die ("can't connect to userdb".mysql_error());
  $username=$_POST['username'];
  $password=$_POST['password'];
  $pwd_again=$_POST['pwd_again'];
  if($username==""||$password=="")
  {
      echo"error:username or password empty";
  }
  else
  {
      if($password!=$pwd_again)
      {
          echo"password is different！";
          echo"<a href='regtest.php'>input again</a>";
      }
      else
      {
      $md5pass=md5($password);
          $sql="insert into user(username,password) values('$username','$md5pass')";
          $result=mysql_query($sql);
          if(!$result)
          {
              echo"Fail reg！".mysql_error();
              echo"<a href='regtest.php'>返回</a>";
          }
          else
          {
              echo"Success reg!";
          }
      }
  }
?>

看下数据库：

登录页面（logintest.php）:

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>welcome to login</title>
</head>
<body>
<form method="post" action="login_check.php">
username:<input type="text" name="username" >
password:<input type="password" name="password">
<input type="submit" value="login">
<input type="reset" value="clean">
<a href="regtest.php" >reg</a>
</form>
</body>
</html>

登陆验证页面（login_check.php）

<?php
$username=$_POST['username'];
$password=$_POST['password'];
$db = mysql_connect("127.0.0.1","root","root") or die("Fail to connect db！");
mysql_select_db("userdb",$db) or die ("Can't connect to userdb".mysql_error());
$sql = "select * from user where username='$username'";
$result = mysql_query($sql);
$column = mysql_fetch_array($result);
if($username == "")
{
    echo"<script type='text/javascript'>alert('input username');location='logintest.php';
            </script>";
}
else
{
   if($password == "")
   {
      echo"<script type='text/javascript'>alert('input password');location='logintest.php';</script>";
   }
   else
   {
      if(($column[username] == $username) && ($column[password] == md5($password)))
      {
         echo"<script type='text/javascript'>alert('Success login!');location='welcome.php?uname=$username';</script>";
      }
      else
          echo"<script type='text/javascript'>alert('username or password error');location='logintest.php';</script>";
   }
}
?>

欢迎页面（welcome.php）

<?php
$username = $_GET['username'];
echo "welcome ".$username."!";
?>

超原始的注册登录完成！还有很多不足，日后再完善！