I am trying to make php emulate a secure realm in abyss.

<?php 
   if (!isset($PHP_AUTH_USER)) 
   { 
      // If empty, send header causing dialog box to appear 
      header('WWW-Autheenticate: Basic realm="My Private Stuff"'); 
      header('HTTP/1.0 401 Unauthorized'); 
      echo 'Authorization Required.'; 
      exit; 
   } 

// If not empty, display values for variables 

else 
   { 

echo " 
      <P>You have entered this username: $PHP_AUTH_USER<br> 
      You have entered this password: $PHP_AUTH_PW<br> 
      The authorization type is: $PHP_AUTH_TYPE</p> 
      "; 

} 

?>

However that produces:
Error 500
Internal Server Error
But if I strip it down to:

  header("WWW-Authenticate: " . 
         "Basic realm=\"Protected Page: " . 
         "Enter your username and password " . 
         "for access.\""); 
  header("HTTP/1.0 401 Unauthorized"); 
  // Display message if user cancels dialog 
  ?> 
  <HTML> 
  <HEAD><TITLE>Authorization Failed</TITLE></HEAD> 
  <BODY> 
  <H1>Authorization Failed</H1> 
  <P>Without a valid username and password, 
     access to this page cannot be granted. 
     Please click ‘reload’ and enter a 
     username and password when prompted. 
  </P> 
  </BODY> 
  </HTML>

It still does not ask me to login, Is there anyway, php or other, to get user validation like:
Error 401
Unauthorized
(This is when no password is entered for console)
Are thier headers being sent that I can/can not change? Does abyss allow secure comunications? Can you help me make this work or is there some otherway way that Abyss supports secure communcations?