How to export html table to excel or pdf in php

In my php page i have a table and if the user requires he has to export that table to excel sheet.. The code for displaying the table is:

$sql=mysql_query("SELECT * FROM attendance WHERE (year = '" . mysql_real_escape_string($_SESSION['year']) . "') and ( branch= '" . mysql_real_escape_string(($_SESSION['branch'])). "') and ( sem= '" . mysql_real_escape_string(($_SESSION['sem'])). "') and (sec= '" . mysql_real_escape_string(($_SESSION['sec'])). "')"); print ""; Print "

"; while($data=mysql_fetch_array( $sql )) < echo " "; > Print "
idno
name
subject
Held Classes
Attended Classes
".$data['idno']."
 
".$data['name'] . " 
".$data['subject']."
 
".$data['heldcls'] . " 
".$data['attendcls']."

 
"; 

how do i export this table to excel sheet. And what should b the code in excel.php. Please help me.. thank you in advance..