<?php

$DBUSER="user";
$DBPASSWD="password";
$DATABASE="user_db";

$filename = "backup-" . $DATABASE . "-" . date("Y-m-d") . ".sql.gz";
$mime = "application/x-gzip";

header( "Content-Type: " . $mime );
header( 'Content-Disposition: attachment; filename="' . $filename . '"' );

$cmd = "mysqldump -u $DBUSER --password=$DBPASSWD $DATABASE | gzip --best";

passthru( $cmd );

exit(0);