How to write mysql quries in php block

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PHP

function insert()
{
$con=mysql_connect("localhost","root","123");
if(!$con)
{
die('COULD NOT CONNECT'.mysql_error());
}
else
{
mysql_select_db("class",$con);
$cmd=mysql_query("insert into myclass values('$_REQUEST[sname]','$_REQUEST[sage]','$_REQUEST[std]','$_REQUEST[sec]','$_REQUEST[per]')",$con);
}
}
insert();


function delete()
{
$con=mysql_connect("localhost","root","123");
if(!$con)
{
die('COULD NOT CONNECT'.mysql_error());
}
else
{
mysql_select_db("class",$con);
$cmd=mysql_query("delete from myclass where name='$_REQUEST[sname]'",$con);
}
}
delete();


function update()
{
$con=mysql_connect("localhost","root","123");
if(!$con)
{
die('COULD NOT CONNECT'.mysql_error());
}
else
{
mysql_select_db("class",$con);
$cmd=mysql_query("update myclass set per='$_REQUEST[per]' where name='$_REQUEST[sname]'",$con);
}
}
update();
?>

This is my code. But this is not execute the user clicked button enent. It defaultly execute any one of this funtion. it's not working the correct button event...any one help me....