php实现网页安全认证的代码详解

<?php
    //unset($_SERVER['PHP_AUTH_USER']);
    $strAuthUser= $_SERVER['PHP_AUTH_USER'];      
    $strAuthPass= $_SERVER['PHP_AUTH_PW'];

 if (! ($strAuthUser == "a" && $strAuthPass == "a")) {
  header('WWW-Authenticate: Basic realm="wly"');
  header('HTTP/1.0 401 Unauthorized');
  echo "用户验证!!";
  exit;
 } else {
  echo "验证通过";
  
  header("location:http://www.baidu.com");
  //unset($_SERVER['PHP_AUTH_USER']);  
 }
?>

<?php
  function authenticate_user() {
    header('WWW-Authenticate: Basic realm="Secret Stash"');
   header("HTTP/1.0 401 Unauthorized");
    exit;
  }
 
  if (! isset($_SERVER['PHP_AUTH_USER'])) {
    authenticate_user();
  } else {
    mysql_pconnect("localhost","authenticator","secret") or die("Can't connect to database server!");
    mysql_select_db("java2s") or die("Can't select authentication database!");
 
   $query = "SELECT username, pswd FROM user WHERE username='$_SERVER[PHP_AUTH_USER]' AND pswd=MD5('$_SERVER[PHP_AUTH_PW]')";
 
    $result = mysql_query($query);
 
    // If nothing was found, reprompt the user for the login information.
    if (mysql_num_rows($result) == 0) {
     authenticate_user();
    }
  }
 ?>