How to create microsoft excel(.xls) worksheet(If u need formatted worksheet)?

<?php
$filepnt = fopen("newfilehtml.xls", 'w+');
$content = '<table border="1"><tr><td bgcolor="#CCCCCC"><b>Id</b></td><td bgcolor="#CCCCCC"><b>Username</b></td></tr> <tr><td>1</td><td>Webmaster</td></tr> <tr><td>2</td><td>mysql_fan</td></tr> <tr><td>3</td><td>slackware</td></tr></table>';
fwrite($filepnt, $content);
fclose($filepnt);
echo '<a href="newfilehtml.xls">Download as .xls</a>';
?>