There are two methods for password protecting the php server - the original used .htacess with simple 401 authentication, but this breaks Kindles and Android devices. Charles later added the ability to authenticate to the server using forms based auth instead - the .htpasswd file can still be used to store the usernames. I know this fixes Android for sure, but I don't have firsthand experience with the Kindle.
Note these options from the config file:
Code:
/*
* Use built-in authentication. The format of the password file is the one
* generated by apache's htpasswd: username:password. Be sure that you
* use an encryption that your installation of PHP supports. Don't put your
* password file into web_dir
*/
$config['use_internal_login'] = false;
$config['password_file'] = 'some path goes here';