Tìm Hiểu về Wordpress - part 38 ppt

9.5.2 Content and File Caching Each time a visitor requests a page from your site, the server kicks into gear, processing scripts and querying the database to generate the page.. 9.5.3 F

all the latest security patches, bug fixes, and script improvements Likewise,

keeping your plugins up-to-date ensures compatibility with the latest versions of

WordPress and helps keep everything running smooth in general

While we’re on the subject, serious WordPress developers and users may benefit

from reading the WordPress Development blog, which is displayed by default

in your WordPress dashboard This is a great place to learn about all the latest

WordPress development news

And, if you happen to discover a bug while working with WordPress, you may

report it at the designated page via the WordPress Codex http://digwp.com/u/328 If

you think that you have discovered a security vulnerability, email the security team

at “security@wordpress.org” with the information and wait for a response before

sharing it anywhere else

9.4.2 Updating WordPress

Those of us who have used WordPress for any length of time understand well

how frequently new versions of WordPress are released When everything goes

according to plan, WordPress is updated four times every year That’s a lot of

upgrading for everyone involved: users, designers, and developers Fortunately,

the busy WordPress devs have integrated an easy way to stay current: automatic

updates from the comfort of the WordPress Admin!

Before WordPress 2.7, upgrading to the latest version of WordPress required

manually uploading files to your server In 2.7 or better, you simply need to

navigate to the “Tools > Upgrade” page of the Admin area and click on the

“Upgrade” button If your server is properly configured and everything goes as

planned, the WordPress core will be updated with a single click!

Likewise for plugins – single-click installs and updates for any plugin listed in the

WordPress Codex To install a plugin, go to “Plugins > Add New” in the Admin

area and knock yourself out There you will be able to search the WordPress Plugin repository and install any plugin by clicking on the “Install” button in the right-hand column Similarly, to update any of your installed plugins, click on the

“update” link when it becomes available Automated convenience at its best

As useful as this is, however, keep in mind that there are several situations where manual upgrades – for core files and/or plugins – are a better way to go about it Here are some scenarios where manual updating might prove more beneficial:

• If you are running an older (pre-2.7) version of WordPress

• If you have a highly customized site with lots of core hacks, mods, etc

• Your server settings forbid this type of behavior

In these and other situations where automatic upgrading is neither possible nor advisable, you should take the time to upgrade manually It isn’t always fun, but staying current is one of the best ways to ensure that your site is kept secure

9.4.3 Logging Changes How do you know if your site has been hacked? If some unscrupulous attacker breaks into your site and injects a few thousand invisible spam links, how would you know? Waiting until your site is penalized by Google is a bad strategy Instead, check out these plugins that will keep an eye on your site and notify you if

anything changes:

• WordPress File Monitor - http://digwp.com/u/330

Monitors your WordPress installation for added/deleted/changed files When a change is detected an email alert can be sent to a specified address

• MonitorHackdFiles - http://digwp.com/u/331

Watches your site, and when it detects a file has changed (or been added), it notifies you via email and tells you which file was changed

Know thy files

If you are automatically

updating your plugins and/

or core files through the Admin

(or any other method), it is

wise to remember that the files

on the server will be newer

than the ones on your local

machine This may sound

totally obvious, but much

confusion and many errors may

be avoided by not overwriting

updated files with older ones

A good way to prevent this is

to either use some sort of a

version control system (such

as Subversion), or else play it

safe and go with the

manual-update method.

• ChangeDetection.com - http://digwp.com/u/332

Free online service that monitors your site and sends you an email/SMS

if anything changes Simple, easy, and effective

9.4.4 Backing Up Your Database and Files

As with all work that is done on a computer, it is essential to ensure

that regular backups are made of your work For dynamically powered

websites such as those powered by WordPress, this practice involves

backing up your database, core files, and added content

The easiest way to keep regular backups of your database is to use the

WP-DBManager plugin http://digwp.com/u/334 This is a powerful backup

plugin that provides a ton of features, including everything from

scheduled database optimizations to completely customized database

backups Backup databases are then stored either on your server or

delivered to you via email This plugin does require a specific server

configuration in order to work, so if things don’t go well, you will need

to either use an alternate plugin or backup your database manually

Fortunately, using a MySQL interface such as phpMyAdmin makes the process

of creating manual backups very easy Simply log in, choose your database from

the left sidebar, and click the “Export” tab From the “Export” page, check the

following settings, which may be different depending on your specific situation:

Another good practice is to backup your physical files These include

the entire WordPress core along with any additional files or content

that you may have added It is a good idea to back up these files

periodically, as well as specifically before any upgrades, updates,

or other modifications To backup your content files automatically,

check out the Content WP Backup plugin: http://digwp.com/u/335

Wait, there is Another…

Although WP DBManager would be our first choice, there is another database plugin called WordPress Database Backup that focuses entirely

on one task: backing up your database Check it out at: http://digwp.com/u/333

9.5.1 Optimizing WordPress

There are many ways to optimize the already-great, out-of-the-box performance

of WordPress Let’s take a look at a few of the most effective ways to improve the speed and consistency of your site

9.5.2 Content and File Caching Each time a visitor requests a page from your site, the server kicks into gear, processing scripts and querying the database to generate the page For sites with small amounts of traffic, the load on your server is probably not a big deal and your pages should load just fine For highly trafficked sites, however, the strain on the server to crank out thousands or millions of pages can really slow things down

A great way to circumvent this problem is to install a caching plugin for your WordPress-powered site A good caching plugin reduces server load by generating

a static copy of each requested page and then delivering that for all subsequent requests Serving static pages requires fewer resources from your server and can speed things up considerably Here are a few of the most popular caching plugins:

• WP Cache - http://digwp.com/u/336

Stores and delivers static versions of your pages Saves work for the database, but still uses the PHP engine to operate

Choose the Right Host

Perhaps the best way to ensure that your site is running as fast, smooth, and consistent as possible is to find the best host More than anything, with web hosting, you get what you pay for If you are serious about running a solid site that is fast and reliable, stay away from cheap, sold-out web hosts and find something with excellent servers and strong service

We can’t stress this enough: a good host is worth the extra money Of course, just because a host costs

more doesn’t necessarily mean that it’s actually better.

Our advice? Do your research, check the message boards, and email your favorite sites for tips and clues

on finding the right host.

• WP Super Cache - http://digwp.com/u/337

Creates static HTML versions of your pages, eliminating the need to invoke PHP

and the database

• DB Cache - http://digwp.com/u/338

Faster performance by caching database queries instead of HTML output

• Batcache - http://digwp.com/u/339

Uses memcached to store and serve rendered pages Not as fast as

WP-Super-Cache but it can be used where file-based caching is not practical or not desired

• Hyper Cache - http://digwp.com/u/340

Stores HTML page output as file content Uses the PHP engine

• AskApache Crazy Cache - http://digwp.com/u/341

Works in tandem with WP-Cache, WP Super Cache, or Hyper Cache to cache

your entire blog

• WP Cache Inspect - http://digwp.com/u/342

Displays information about cached content and provides useful options

for management

It is important to read the documentation carefully before installing any of these

caching plugins In general, caching is a process that fundamentally affects the

way your site performs, so it is important to understand the pros and cons of each

plugin as well as the requirements for installation You definitely should not try to

combine caching plugins unless you really know what you’re doing And even then,

we don’t recommend it

One thing to keep in mind is that there are some common downsides to using

WP Cache, WP Super Cache, and some of the others, namely the inability to track

certain page statistics, outdated content displayed in sidebars, and other issues

involved with trading dynamic functionality with static page delivery

9.5.3 File Compression Methods Another excellent way to improve performance while also saving bandwidth is

to compress your web pages and other site content Compression does exactly what you would expect: files and content are compressed by the server in order

to reduce their overall size Once the content is received by the browser, it is immediately uncompressed and displayed properly This results in faster loading times and reduced bandwidth usage

While a complete excursion into the realms of file compression is well beyond the scope of this book, here are a few ideas to get you started in the right direction:

• File compression via Apache’s gzip module - for servers running older

versions of Apache, an easy and effective way to compress your content is to enable mod_gzip via your server configuration or root .htaccess file

• File compression via Apache’s deflate module - for servers running newer

versions of Apache, an easy and effective way to compress your content is to enable mod_deflate via your server configuration or root .htaccess file

• File compression via PHP - It is also possible to compress your files using PHP’s

output buffer This method usually involves adding a small snippet of code to the beginning of your theme’s header.php file

• Manual file compression - For JavaScript, CSS, and other static files, it is also

possible to implement compression manually This typically requires gzipping the files in question and then delivering them via targeting script to supportive browsers

• Minifying CSS and JavaScript files - Apart from compressing the actual file,

it is also possible to compress the contents of your CSS and JavaScript files This

process is called “minifying” and usually involves removing as much white-space

as possible For JavaScript, there are also additional techniques that further reduce the size of the file

Spoiled rotten, WordPress users enjoy such awesomely useful plugins as WP

Minify http://digwp.com/u/344 and PHP-Speedy http://digwp.com/u/345 that will minify, compress, combine, and cache your CSS and JavaScript files There are also some

great online services for compressing CSS and JavaScript file content, including

these great sites:

• YUI Compressor - http://digwp.com/u/347

• Dean Edwards Packer - http://digwp.com/u/346

• JavaScript Compressor - http://digwp.com/u/349

• Another JavaScript Compressor - http://digwp.com/u/348

• Styleneat.com - http://digwp.com/u/350

• JSMin - http://digwp.com/u/351

While there are many different ways to take advantage of file compression, your

implementation will depend on the tools and resources available to your server If

possible, enable mod_gzip or mod_deflate and forget about it Otherwise, if these

modules are not available to you, there are many other solutions available

9.5.4 Optimizing CSS and JavaScript

If all that server/database compression/optimization stuff leaves you gasping for air,

relax – a significant amount of optimization can be accomplished by focusing on

the code and content used to create the user interface By optimizing the content

of JavaScript, CSS, and even HTML files, you can reduce file size, save bandwidth,

and reduce loading times for visitors Here are some key strategies that will help

you to optimize various types of code:

• Keep your code clean! - Eliminate unnecessary comments and superfluous

markup Focus on clean, well-written code and you will have a strong

foundation for optimizing your pages

• Keep HTTP requests to a minimum - One of the best ways to improve the

loading times for your pages is to reduce the number of HTTP requests to the

server Every JavaScript file, CSS file, and image requires its own HTTP request

and thus slows down loading time By consolidating multiple CSS and JavaScript

files and implementing “sprite” techniques, you can reduce the number of HTTP

Optimize with WP CSS

If you don’t mind an additional plugin to optimize your CSS files, you’ll want to check out WP-CSS.

WP-CSS uses a shorthand technique to strip extraneous whitespace from your CSS files Then after reducing file size, WP-CSS compresses your CSS files with Apache’s powerful gzip compression It even includes any @import files into the mix.

http://digwp.com/u/355

Easy PHP Compression

More information on how to compress your files with PHP:

http://digwp.com/u/343

requests and increase the performance of your site.

• Use sprites for images - Put simply, sprites are multiple images consolidated

into a single image By strategically placing different images in a single image file, we decrease latency in visual display while also reducing the overall number

of HTTP requests Sprites are commonly used together with CSS to create stunning and effective rollover effects, background imagery, and more

• Include your stylesheets at the top of your pages - When including

external stylesheets in your pages, be sure to include them at the top of the

page in the <head> section This will enable browsers to render your pages

progressively, which makes them appear to load much faster than they would

otherwise

• Include JavaScript at the bottom of your pages - When including external

JavaScript files, placing them at the bottom of the page, just before the closing

<html> element, ensures that your clients’ browsers are able to download the maximum number of components, decreasing load times and improving performance

• Validate your code! - One of the best ways to ensure that you are adhering to

the principles of modern web design and web standards is to check your code with an online validator After checking your page, the validator will return

a report telling you either that your code has passed with flying colors, failed miserably, or anything in-between If there are problems with your code, the validator will explain each issue and provide suggestions for fixing them

There are many different validators available depending on code type, however, the W3C (World Wide Web Consortium) provides just about everything you need right under one roof Here are some URLs for two of their free

code-validation services:

• W3C (X)HTML Validator - http://digwp.com/u/353

• W3C CSS Validator - http://digwp.com/u/354

Spriting Made Easy

Creating sprites is an art form

that many have yet to master

Thankfully, designers now

have a free online service that

automagically creates sprites

for you:

http://digwp.com/u/352

9.5.5 Reducing the Number of HTTP Requests

One of the biggest factors of site performance is the number of HTTP requests that

your pages are making to the server Each request for a CSS file, JavaScript file,

image, or any other external file requires a separate call to the server, which then

must acknowledge, process, and return the requested file When you have too

many files linked to a document, either in the <head> area or in the content itself,

your site’s performance may be negatively affected This effect is easily seen by

comparing the load times of sites that include many different CSS and JavaScript

files with sites that have taken appropriate measures to reduce the overall number

of requests made by their pages Here are a few tips for reducing the number of

HTTP requests made by your site:

• Eliminate unnecessary files - Anything that you are calling from your web

page that is not absolutely essential should be cut out from the picture When

possible, replace design-related images such as rounded borders with pure CSS

alternatives

• Consolidate CSS files - Instead of linking to five different CSS files, combine

them into a single, optimized file If you’re not sure, check your source code -

you may be surprised to find that some of your plugins are calling additional

CSS files

• Consolidate your JavaScript files - As with your CSS files, combine

multiple JavaScript files into a single, optimized file Check your source code

and consolidate anything that you can get your hands on Just make sure to

preserve the order of appearance of the various scripts

• Use image sprites - If your theme design makes heavy use of images, the

number of HTTP requests may be very high indeed Check your design and look

at the images being used If any of them can be combined into a single image,

then try to do so Granted, combining images into so-called “sprites” is a bit

of a dark art, but with a little research and some practice, you will find the

reward of improved performance to be well worth the effort A great example

of image sprites is seen with social-media icons that have been combined into

a single file and then positioned differently for each link with a little CSS This

one technique can drastically cut down on requests and help speed things up

Hey Look, it’s a Sprite!

In this social-media sprite, all of the icons are contained within a single, transparent PNG and simply shifted with CSS to display the appropriate image being called.

How to Stop Leeching and Improve

Site Performance

As explained in section 9.1.10 of this chapter, “hotlinking” is bandwidth theft that happens whenever another site is linking directly to your files For example, if you have some spicy picture of Chewbacca in a swimsuit, you may quickly discover that unscrupulous bastards are linking directly to it, stealing your image, your bandwidth, and your traffic To prevent this sort of leeching, add the following slice of HTAccess code to your site’s root htaccess

file (or Apache configuration file):

# HOTLINK PROTECTION

<IfModule mod_rewrite.c>

RewriteEngine on

RewriteCond %{HTTP_REFERER} !^$

RewriteCond %{REQUEST_FILENAME} -f

RewriteCond %{REQUEST_FILENAME} \.(gif|jpe?g?|png)$ [NC]

RewriteCond %{HTTP_REFERER} !^https?://([^.]+\.)?domain\ [NC]

RewriteRule \.(gif|jpe?g?|png)$ - [F,NC,L]

</ifModule>

There are of course many ways to customize this code, including changing the domain name to match your own, adding additional approved domains to the list (so your images

are visible in feed readers, for example), and so on As-is, this code simply returns a 403

Forbidden error for anything other than your site that is requesting images This may be

changed to return some nasty image, so that people who try to steal your zesty picture

of Chewbacca will get some nasty shot of your armpit instead Currently, this code blocks hotlinking for GIFs and JPGs, but you can add many other types of files to the list as well For a more comprehensive look into the fine art of protecting your site against hotlinking, check out http://digwp.com/u/294