PHP: force download file

gistfile1.php

<?php
function force_download($filename = '', $data = '')
	{
		if ($filename == '' OR $data == '')
		{
			return FALSE;
		}

		// Try to determine if the filename includes a file extension.
		// We need it in order to set the MIME type
		if (FALSE === strpos($filename, '.'))
		{
			return FALSE;
		}

		// Grab the file extension
		$x = explode('.', $filename);
		$extension = end($x);

		// Load the mime types
		if (defined('ENVIRONMENT') AND is_file(APPPATH.'config/'.ENVIRONMENT.'/mimes.php'))
		{
			include(APPPATH.'config/'.ENVIRONMENT.'/mimes.php');
		}
		elseif (is_file(APPPATH.'config/mimes.php'))
		{
			include(APPPATH.'config/mimes.php');
		}

		// Set a default mime if we can't find it
		if ( ! isset($mimes[$extension]))
		{
			$mime = 'application/octet-stream';
		}
		else
		{
			$mime = (is_array($mimes[$extension])) ? $mimes[$extension][0] : $mimes[$extension];
		}

		// Generate the server headers
		if (strpos($_SERVER['HTTP_USER_AGENT'], "MSIE") !== FALSE)
		{
			header('Content-Type: "'.$mime.'"');
			header('Content-Disposition: attachment; filename="'.$filename.'"');
			header('Expires: 0');
			header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
			header("Content-Transfer-Encoding: binary");
			header('Pragma: public');
			header("Content-Length: ".strlen($data));
		}
		else
		{
			header('Content-Type: "'.$mime.'"');
			header('Content-Disposition: attachment; filename="'.$filename.'"');
			header("Content-Transfer-Encoding: binary");
			header('Expires: 0');
			header('Pragma: no-cache');
			header("Content-Length: ".strlen($data));
		}

		exit($data);
	}
?>