Restrict characters on registration

[M.W.S.]

<?php echo "Hello World" ?>

How to restrict characters on registration of in textfields?

 

Thanks!

[sspoke]

regular expressions

 

I use this

 

foreach($_POST as $field => $value)

{

if (ereg("(Name)",$field))

{

if (!ereg("^[A-Za-z' -]{1,50}$",$value))

{

unset ($_GET['do']);

$message_new = "$field is not a valid name, please check and try again.";

header("Location:index.php?page=register");

exit();

}

}

$$field = strip_tags(trim($value));

}