Update: I’ve made this into a plugin for those interested. You can post any issues here.

There’s been a whole heap of discussions recently about the correct way to load jQuery. I thought I’d throw my solution into the ring (which is in-use on this site right now). Here’s what I have; I’ll explain below:

function zslabs_scripts() {
if (!is_admin()) {
// Enqueue the core jQuery script (just in-case)
wp_enqueue_script('jquery');
// Get current version of jQuery from WordPress core
$wp_jquery_ver = $GLOBALS['wp_scripts']->registered['jquery']->ver;
// Figure out which protocol to use
$http_protocol = is_ssl() ? 'https:' : 'http:';
// Set Google jQuery URL
$jquery_google_url = $http_protocol.'//ajax.googleapis.com/ajax/libs/jquery/'.$wp_jquery_ver.'/jquery.min.js';
// Setup Curl Function
function jquery_get_data($url) {
$ch = @curl_init($url);
@curl_setopt($ch, CURLOPT_HEADER, TRUE);
@curl_setopt($ch, CURLOPT_NOBODY, TRUE);
@curl_setopt($ch, CURLOPT_FOLLOWLOCATION, FALSE);
@curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
$status = array();
preg_match('/HTTP\/.* ([0-9]+) .*/', @curl_exec($ch) , $status);
return ($status[1] == 200);
}
// Determine if Google jQuery URL is available
if (jquery_get_data($jquery_google_url)) {
wp_deregister_script('jquery');
wp_register_script('jquery', ''.$jquery_google_url.'', '', $wp_jquery_ver, false);
}
}
}

add_action('wp_enqueue_scripts', 'zslabs_scripts');

Alright kiddies, here we go:

First, we create a function to hold our scripts:

function zslabs_scripts() { }

Since we only want this to effect the front-end of the website, we do a quick check to make sure we’re not in the admin:

if (!is_admin()) {}

Next, let’s make sure that the core jQuery library is loaded (in-case any naughty themes or plugins have deregistered it):

wp_enqueue_script('jquery');

Next, using the global $wp_scripts variable, we’ll get the version of jQuery included in the WordPress core:

$wp_jquery_ver = $GLOBALS['wp_scripts']->registered['jquery']->ver;

Next, we’ll use the handy-dandy is_ssl() function to determine if the site is using SSL or not:

$http_protocol = is_ssl() ? 'https:' : 'http:';

Next, we’ll create the variable that’ll hold the Google jQuery URL:

$jquery_google_url = $http_protocol.'//ajax.googleapis.com/ajax/libs/jquery/'.$wp_jquery_ver.'/jquery.min.js';

So – what we’re doing above is substituting in both the http protocol and version number as part of the Google URL string – genius!

Next, we’ll setup the CURL function to determine if a URL is available or not:

function jquery_get_data($url) {
$ch = @curl_init($url);
@curl_setopt($ch, CURLOPT_HEADER, TRUE);
@curl_setopt($ch, CURLOPT_NOBODY, TRUE);
@curl_setopt($ch, CURLOPT_FOLLOWLOCATION, FALSE);
@curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
$status = array();
preg_match('/HTTP\/.* ([0-9]+) .*/', @curl_exec($ch) , $status);
return ($status[1] == 200);
}

After that – we can create a simple if statement to determine if the Google URL is available or not and if it is, do the magic:

if (jquery_get_data($jquery_google_url)) {
wp_deregister_script('jquery');
wp_register_script('jquery', ''.$jquery_google_url.'', '', $wp_jquery_ver, false);
}

What we’re doing above is deregistering the core WordPress jQuery file (it’s okay – don’t freak out yet) and then reregister jQuery (using the same handler), but substituting in our Google URL.

Lastly, close out the function and wrap that baby in a wp_enqueue_scripts action:

add_action('wp_enqueue_scripts', 'zslabs_scripts');

So – why is this awesome? Well, it solves a few issues that others ran into issues with (and addresses some that other theme/plugin developers have had):

• Loads jQuery from Google only if it’s available
• Uses the identical jQuery version from Google that WordPress has available in your WP install (this was the big one)
• Checks and makes sure to use the correct http protocol
• Looks a hell of a lot cleaner if you view the source
• I made it

I’m sure this could use some improvements – so if anyone has any suggestions, I’m certainly open to anything that would make this better. Thanks!