Download.php

<?php

// Set the file size header
header( "Content-Length: " . @filesize( $file_path ) );

// Now deliver the file based on the kind of software the server is running / has enabled
if ( stristr( getenv( 'SERVER_SOFTWARE' ), 'lighttpd' ) ) {

	header( "X-LIGHTTPD-send-file: $file_path" );

} elseif ( $direct && ( stristr( getenv( 'SERVER_SOFTWARE' ), 'nginx' ) || stristr( getenv( 'SERVER_SOFTWARE' ), 'cherokee' ) ) ) {

	// We need a path relative to the domain
	$redirect_path = '/' . str_ireplace( realpath( $_SERVER['DOCUMENT_ROOT'] ), '', $file_path );
	$redirect_path = apply_filters( 'edd_sl_accel_redirect_path', $redirect_path, $file_path );
	header( "X-Accel-Redirect: $redirect_path" );

}

if( $direct ) {

	edd_deliver_download( $file_path );

} else {

	// The file supplied does not have a discoverable absolute path
	edd_deliver_download( $requested_file, true );

}