Please help with with Regex Pattern

I'm trying to match following url but couldn't come up with right pattern.
www.blahblahblah.com/show/index.php?product=item1

I just want to match this part only from the html
www.blahblahblah.com/show/index.php?product=

I tried following but didn't work-
$pattern = /www.blahblahblah.com\/show\/index.php\?product=/

but didn't work. Plz co-operate.

Actually you don't need to use regex if you only want to match those urls.
Try strstr()

Example:

$url = "www.blahblahblah.com/show/index.php?product=item1";

$pattern = "www.blahblahblah.com/show/index.php?product=";

$result = strstr($url, $pattern);
if($result == true) {
echo 'true';
} else {
echo 'false';
}


Output: true