getting query string from PPC

[smallcompany]

You have traffic coming to your site from Yahoo PPC, Google AdWords or MSN adCenter. How do you strip down the referrer link to a search query so you get something like

$qr = search_query

[smallcompany]

ok.

$ref = $_SERVER["HTTP_REFERER"]
if (strstr($ref, "google.com/search?")) {
$search_query = "";
$query_arg = strtok($ref, "&");
while ($query_arg!== false) {
if (strstr($query_arg, "q=")) {
$search_query = substr($query_arg, 2);
break;
}
$query_arg = strtok("&");
}
echo $search_query;
}

Why is this failing on line #2?

Thanks

[eelixduppy]

This should get you somewhere:
[webmasterworld.com...]

:)