Simple Multilanguage functionality

multilanguage.php

<?php
define('LANGUAGES_PATH', 'languages/');
define('DEFAULT_LANGUAGE', 'en');
define('LANGUAGE_COOKIE_TIME', 1314000 ); // 3600 * 365 = 1314000; (1 year)
define('COOKIE_DOMAIN', '.xaviesteve.com');

/*

Usage:

$dict = new Dictionary;
$dict->_( 'Click here' );
$dict->_( 'Hello %1', array('Xavi') );


languages/en.php:

<?php

$dictionary = array(
	'ln' 		=> 'en',
	'Click here' => 'Click here',
);

*/
Class Dictionary {

	private $dictionary = [];

	// Stores and returns the language
	function __construct( $ln = false )
	{
		// if language has been specified then just return that
		if ( $ln )
		{
			$this->load( $ln );
		}
		else
		{
			$this->load( $this->detect() );
		}
		return $this->dictionary;
	}


	// Find out the language
	private function detect()
	{
		// GET / POST parameter
		if ( isset( $_REQUEST['ln'] ) AND $this->is_valid_ln( $_REQUEST['ln'] ) )
		{
			$_COOKIE['ln'] = $_GET['ln'];
			setcookie( 'ln', $_GET['ln'], time() + LANGUAGE_COOKIE_TIME, '/', COOKIE_DOMAIN );
			$ln = $_GET['ln'];
		}

		// Cookie
		else if ( isset( $_COOKIE['ln'] ) AND $this->is_valid_ln( $_COOKIE['ln'] ) )
		{
			$ln = $_COOKIE['ln'];
		}

		// If browser-specified
		else if ( isset( $_SERVER['HTTP_ACCEPT_LANGUAGE'] ) AND $this->is_valid_ln( strpos( $_SERVER['HTTP_ACCEPT_LANGUAGE'], 0, 2 ) ) )
		{
			$ln = explode( ",", $_SERVER['HTTP_ACCEPT_LANGUAGE'] );
		}
		else
		{
			$ln = DEFAULT_LANGUAGE;
		}
		return $ln;
	}




	private function load( $ln = false )
	{
		if ( $this->is_valid_ln( $ln ) )
		{
			require LANGUAGES_PATH . $ln . '.php';
			$this->dictionary = $dictionary;
		}
		else
		{
			require LANGUAGES_PATH . DEFAULT_LANGUAGE . '.php';
			$this->dictionary = $dictionary;
		}
		return $this->dictionary;
	}

	private function is_valid_ln( $ln = false )
	{
		return file_exists( LANGUAGES_PATH . $ln . '.php' );
	}




	public function _( $string, $vars = array() )
	{
		if ( isset( $this->dictionary ) AND isset( $this->dictionary[ $string ] ) )
		{
			$return = $this->dictionary[ $string ];
		}
		else
		{
			$return = $string;
		}

		$i = 1;

		foreach ($vars as $var) {
			$return = str_replace( '%' . $i, $vars[ $i-1 ], $return );
			$i++;
		}

		return $return;
	}

}