Problem in passing value

Dear all,

I am using Apache and PHP as local web server.

I have the following script as show.php

<?
    if ($a==1) {
        echo "True."
    } else {
        echo "False."
    }
?>

However, when I type http://localhost/show.php?a=1, it shows "True.", why?
Is there any problem in my setting of Apache server?

Can anyone help me? Thank you.