php does not let me override default parameter
<p>I can't seem to get php to accept dynamic values for parameters when I have a default specified. I've read <a href="http://stackoverflow.com/questions/9166914/php-using-default-arguments-in-a-function">here</a> that the default value needs to be at the end of the function, which I've done.</p>

<pre><code>$isbilling = true;

function retrieve_address($dbh, $customer_id, $isbilling=false){
echo $isbilling; //false
}
</code></pre>

<p>What am I doing wrong here?</p>
