para aprender a usar bien ereg() y poder validar bien tus formularios checa esta url
http://www.developers-resources.com/stories.php?story=01/10/25/0549771
<a href='ir.asp?http://www.developers-resources.com/stories.php?story=01/10/25/0549771' target='_blank'>http://www.developers-resources.com/stor...</a>
adios