Question

Is there any way to differentiate IE7 versus IE6 using PHP’s get_browser() function?

Answer 1

You can do so as such:

$browser = get_browser();

if($browser->browser == 'IE' && $browser->majorver == 6) {
    echo "IE6";
} elseif($browser->browser == 'IE' && $browser->majorver == 7) {
    echo "IE7";
}

A quick look to the official get_browser() documentation would of answered your question. Always read the documentation before.