Basic Security

<?php 
  
  // START FILE: security.php 
  session_start(); 
  $errorlogin     = "Authentication Required"; // Text to display when login error 
  $basicrealm     = "Private Stuff"; // Displayed text on login form 
  $authentication = Array (1=>Array("user1", "pass1"), // User and Pass for User-1 
                           2=>Array("user2", "pass2"), // User and Pass for User-2 
                           3=>Array("user3", "pass3"));// User and Pass for User-3 

  class security { 
    var $authentication = Array(); 
    var $errorlogin; 
    var $basicrealm; 
    function security() { 
      global $authentication, $errorlogin, $basicrealm; 
      $this->authentication = $authentication; 
      $this->errorlogin     = $errorlogin; 
      $this->basicrealm     = $basicrealm; 
    } 
    function secureMe() { 
      global $_SESSION, $PHP_AUTH_USER, $PHP_AUTH_PW; 
      if (trim($PHP_AUTH_USER)!=""&&trim($PHP_AUTH_PW)!="") { 
        if($this->checkLogin($PHP_AUTH_USER, $PHP_AUTH_PW)) return true; 
      } 
      if (!$_SESSION||$_SESSION["passed"]!="") { 
        $this->showLogin(); 
        return false; 
      } 
    } 
    function showLogin() { 
      global $login_error, $realms; 
      header('WWW-Authenticate: Basic realm='.$this->basicrealm); 
      header('HTTP/1.0 401 Unauthorized'); 
      print $this->errorlogin; 
      exit();   
    } 
    function checkLogin($username, $password) { 
      for($i=0;$i<count($this->authentication);$i++) { 
        if($username == $this->authentication[$i][0] && 
           $password == $this->authentication[$i][1]) { 
          $j++; 
        } 
      } 
      if($j!=0) return true; 
    } 
  }; 
  // END FILE: security.php 
?> 

Put the line below on the top of the page you wish to secured. 

<?php 
  require_once("./security.php"); 
  $security = new security; 
  if($security->secureMe()) $passed = "true"; session_register('passed'); 
?>