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HTTP authentication with PHP

It is possible to use the header() function to send an "Authentication Required" message to the client browser causing it to pop up a Username/Password input window. Once the user has filled in a username and a password, the URL containing the PHP script will be called again with the predefined variables PHP_AUTH_USER, PHP_AUTH_PW, and AUTH_TYPE set to the user name, password and authentication type respectively. These predefined variables are found in the $_SERVER array. Both "Basic" and "Digest" (since PHP 5.1.0) authentication methods are supported. See the header() function for more information.

An example script fragment which would force client authentication on a page is as follows:

Example #1 Basic HTTP Authentication example

if (!isset($_SERVER['PHP_AUTH_USER'])) {
header('WWW-Authenticate: Basic realm="My Realm"');
header('HTTP/1.0 401 Unauthorized');
'Text to send if user hits Cancel button';
} else {
"<p>Hello {$_SERVER['PHP_AUTH_USER']}.</p>";
"<p>You entered {$_SERVER['PHP_AUTH_PW']} as your password.</p>";

Example #2 Digest HTTP Authentication example

This example shows you how to implement a simple Digest HTTP authentication script. For more information read the » RFC 2617.

'Restricted area';

//user => password
$users = array('admin' => 'mypass''guest' => 'guest');

if (empty(
header('HTTP/1.1 401 Unauthorized');
header('WWW-Authenticate: Digest realm="'.$realm.

'Text to send if user hits Cancel button');

// analyze the PHP_AUTH_DIGEST variable
if (!($data http_digest_parse($_SERVER['PHP_AUTH_DIGEST'])) ||
'Wrong Credentials!');

// generate the valid response
$A1 md5($data['username'] . ':' $realm ':' $users[$data['username']]);
$A2 md5($_SERVER['REQUEST_METHOD'].':'.$data['uri']);
$valid_response md5($A1.':'.$data['nonce'].':'.$data['nc'].':'.$data['cnonce'].':'.$data['qop'].':'.$A2);

if (
$data['response'] != $valid_response)
'Wrong Credentials!');

// ok, valid username & password
echo 'You are logged in as: ' $data['username'];

// function to parse the http auth header
function http_digest_parse($txt)
// protect against missing data
$needed_parts = array('nonce'=>1'nc'=>1'cnonce'=>1'qop'=>1'username'=>1'uri'=>1'response'=>1);
$data = array();
$keys implode('|'array_keys($needed_parts));

preg_match_all('@(' $keys ')=(?:([\'"])([^\2]+?)\2|([^\s,]+))@'$txt$matchesPREG_SET_ORDER);

    foreach (
$matches as $m) {
$data[$m[1]] = $m[3] ? $m[3] : $m[4];

$needed_parts false $data;

Note: Compatibility Note

Please be careful when coding the HTTP header lines. In order to gu