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PHP: Enqueue Google CDN jQuery with fallback to WordPress
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<?php | |
add_action( 'wp_enqueue_scripts', 'wps_enqueue_jquery' ); | |
/** | |
* Enqueue jQuery from Google CDN with fallback to local WordPress | |
* | |
* @link http://codex.wordpress.org/Function_Reference/wp_enqueue_script | |
* @link http://codex.wordpress.org/Function_Reference/wp_register_script | |
* @link http://codex.wordpress.org/Function_Reference/wp_deregister_script | |
* @link http://codex.wordpress.org/Function_Reference/get_bloginfo | |
* @link http://codex.wordpress.org/Function_Reference/is_wp_error | |
* @link http://codex.wordpress.org/Function_Reference/set_transient | |
* @link http://codex.wordpress.org/Function_Reference/get_transient | |
* | |
* @uses get_transient() Get the value of a transient. | |
* @uses set_transient() Set/update the value of a transient. | |
* @uses is_wp_error() Check whether the passed variable is a WordPress Error. | |
* @uses get_bloginfo() returns information about your site. | |
* @uses wp_deregister_script() Deregisters javascripts for use with wp_enqueue_script() later. | |
* @uses wp_register_script() Registers javascripts for use with wp_enqueue_script() later. | |
* @uses wp_enqueue_script() Enqueues javascript. | |
*/ | |
function wps_enqueue_jquery() { | |
// Setup Google URI, default | |
$protocol = ( isset( $_SERVER['HTTPS'] ) && 'on' == $_SERVER['HTTPS'] ) ? 'https' : 'http'; | |
// Get Latest Version | |
$url = $protocol . '://code.jquery.com/jquery-latest.min.js'; | |
// Get Specific Version | |
//$url = $protocol . '://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js'; | |
// Setup WordPress URI | |
$wpurl = get_bloginfo( 'wpurl') . '/wp-includes/js/jquery/jquery.js'; | |
// Setup version | |
$ver = null; | |
// Deregister WordPress default jQuery | |
wp_deregister_script( 'jquery' ); | |
// Check transient, if false, set URI to WordPress URI | |
delete_transient( 'google_jquery' ); | |
if ( 'false' == ( $google = get_transient( 'google_jquery' ) ) ) { | |
$url = $wpurl; | |
} | |
// Transient failed | |
elseif ( false === $google ) { | |
// Ping Google | |
$resp = wp_remote_head( $url ); | |
// Use Google jQuery | |
if ( ! is_wp_error( $resp ) && 200 == $resp['response']['code'] ) { | |
// Set transient for 5 minutes | |
set_transient( 'google_jquery', 'true', 60 * 5 ); | |
} | |
// Use WordPress jQuery | |
else { | |
// Set transient for 5 minutes | |
set_transient( 'google_jquery', 'false', 60 * 5 ); | |
// Use WordPress URI | |
$url = $wpurl; | |
// Set jQuery Version, WP stanards | |
$ver = '1.8.2'; | |
} | |
} | |
// Register surefire jQuery | |
wp_register_script( 'jquery', $url, array(), $ver, true ); | |
// Enqueue jQuery | |
wp_enqueue_script( 'jquery' ); | |
} |
Like the other gents were mentioning there are some flaws using the technique described here.
- Sure it seems fine to 'just' fetch the head request, but that's a request for every request on your site or even server.
- Do you really want to delay your script output the time it takes to connect to a remote host? This could be up to the timeout limit (default 2 seconds).
- If your server can connect to the CDN in a certain time, it is by no means a guarantee that the client will as well.
These are things you learn when working with high-volume servers and can be a server/website killer.
Which leads to a solution I came up with (which can be improved on) using a fairly common method of JavaScript fallback in the following gist: https://gist.github.com/moorscode/b04e648200c844bf3f6d
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Here's an article with great advice on how to handle this correctly : http://www.hanselman.com/blog/CDNsFailButYourScriptsDontHaveToFallbackFromCDNToLocalJQuery.aspx