wps_enqueue_jquery.php

<?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' );
}