form validation using php

hi

i need to validate a field in a form where a user enters their lodgement
number as part of a registration form. this lodgement number can have
letters, numbers, spaces and special characters. i do not know exactly what
those special characters are, so do i have to define the type of special
characters and validate accordingly.

presently my php code for validating the lodgement number is

$lodgementtf  = $_POST["lodgementtf"];

if($lodgementtf == "" || !preg_match("/^[a-zA-Z0-9_ <]+$/", $lodgementtf) )

{
echo "display error message":
}

i also have another way of validating

if($lodgementnumber == "" || !preg_match("/^[a-zA-Z0-9_ !-@£$%^&*()]+$/",
$lodgementnumber) )

does this mean that the special characters can only be = a space AND
_!-@£$%^&*() and no other special characters.

please advice.

thanks.