Enqueueing jQuery from Google's CDN with local fallback in WordPress

functions.php

function rd_bulletproof_jquery() {
$protocol = ($_SERVER['HTTPS'] == 'on') ? 'https' : 'http';
$url = $protocol . '://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js';
wp_deregister_script('jquery');
if (get_transient('google_jquery') == true) {	    
	wp_register_script('jquery', $url, array(), null, true);
} 
else {
	$resp = wp_remote_head($url);
	if (!is_wp_error($resp) && 200 == $resp['response']['code']) {
		set_transient('google_jquery', true, 60 * 5);
		wp_register_script('jquery', $url, array(), null, true);
	} 
	else {
		set_transient('google_jquery', false, 60 * 5);
		$url = get_bloginfo('wpurl') . '/wp-includes/js/jquery/jquery.js';
		wp_register_script('jquery', $url, array(), '1.7.1', true);
	}
}
wp_enqueue_script('jquery');
/* Any other Javascript would be enqueued here */
}
add_action('wp_enqueue_scripts', 'rd_bulletproof_jquery');