Here’s an excerpt:

The concert hall at the Syndey Opera House holds 2,700 people. This blog was viewed about 46,000 times in 2011. If it were a concert at Sydney Opera House, it would take about 17 sold-out performances for that many people to see it.

Click here to see the complete report.

We often fail to realize how little we know about a thing until we attempt to simulate it on a computer.
Donald E. Knuth
The Art of Computer Programming, Volume 1, Third Edition
Section 2.2.5, Exercise 10 (p. 298) 

The setup:

• index.php
• wp-blog-header.php: wp();
• wp-includes/functions.php: function wp
• wp-includes/class-wp.php: function main
• wp-includes/class-wp.php: function parse_request
• $rewrite = $wp_rewrite->wp_rewrite_rules() (add bbPress)

The magic:

foreach ( $rewrite as $match => $query ) {
	if ( preg_match("#^$match#", $request_match, $matches) ) {
		// Got a match.
		$this->matched_rule = $match;
		break;
	}
}

The real voodoo is in creating the rewrite rules. Example: bbPress

• register_post_types
• register_taxonomies
• add_rewrite_tags
• generate_rewrite_rules

Exercise: optimize parse_request by restructuring the rules into a tree.

Nacin suggests: wp-hackers Skip Main Query

• the grand scheme of things (png, blog post)
• $wp->init()
• class freshlypressed_wp extends wp
• wp() calls $wp->main()
• $wp->main() calls $this->parse_request()
• $this is a freshlypressed_wp

Problems:

• Can’t extend a variable class (class my_wp extends $wp_class)
• No pluggable inheritance chaining
• No way for several plugins to cooperatively extend a class

This is where you come in. As a core contributor or plugin developer, you are aware of areas in WordPress code that scare you. I’ve been there and back again. I’ve digested, debugged and patched some of the most labyrinthine logic. I’ve even written some of the worst of it. On Saturday, August 13, I will try to make sense of it for everyone.

Please take a minute to recall something in the core code of WordPress that really stumps you. Ask me about it. I will try to work all of your comments into my talk, provided that I can’t answer it with a quick reply, a link to the Codex or a Google search.

If this gambit of asking for questions beforehand fails, maybe I’ll just give a tour of my personal favorite fork of WordPress in which every function block is shaped like a pony. (Please don’t let that happen.)

The admin bar on my self-hosted blog.

Stats 1.8 adds a tiny bar chart (called a “sparkline”) to the admin bar. To make this chart more interesting, and not just a copy of what you can already see in your stats report page, we zoomed in on the time axis. Rather than show one data point per day we show each of the last 48 hours. Following your blog’s time zone setting, lighter and darker bars represent daylight and nighttime hours.

Design credit goes to Joen and MT. The sparkline design seems simple and obvious now, but it took a lot of tries to get it that way. It wouldn’t have happened without their contributions.

Of course, we intend to bring the new sparkline to the WordPress.com admin bar as soon as possible. Remember how we said the plugin’s stats reports are a few versions behind the WordPress.com reports? With the admin bar it’s the reverse. Self-hosted bloggers are the first to get this upgrade. Everyone on WordPress.com will have it soon.

by Ulf Wendel, on Flickr

Everybody loves PHP’s sprintf(). We use it everywhere. There are just some things it doesn’t do, like format lists in sentences. Three years ago, while working on the Media Library, I needed a way to list categories or tags in a sentence. And, by golly, it would need Oxford commas and localization to be worthy of WordPress.

Problem solved

I wrote wp_sprintf() as a wrapper for sprintf(). It uses WordPress filters to customize the formatting directives. WordPress only uses this in one place, the function where I needed to list categories and tags: get_the_taxonomies(). This is used in standard template tags so I estimate wp_sprintf() has run at least a trillion times without fanfare. The time has come to give wp_sprintf() the attention it deserves.

wp_sprintf

The calling interface is identical to sprintf():

string wp_sprintf ( string $format [, mixed $args [, mixed $... ]] )

Internally, wp_sprintf() splits the format string into fragments that begin with a single ‘%’. It sends each fragment through the 'wp_sprintf' filter with the appropriate $args, respective of numbered directives (‘%1$s’). If the filter did not modify the fragment, it is passed through sprintf(). The processed fragments are concatenated and then returned.

Functionally, wp_sprintf() should be identical to sprintf() until a filter is added which implements a new formatting directive, or supersedes any of the standard ones. It is certainly less optimized so it should only be used when a customized directive is needed.

wp_sprintf_l

The only 'wp_sprintf' filter now in core is wp_sprintf_l(), which adds a new directive to format arrays into lists, %l:

wp_sprintf('%s: %l.', 'Tags', array('Cats', 'Dogs', 'Birds'));
=> 'Tags: Cats, Dogs, and Birds.'

Our filter, wp_sprintf_l(), receives a format fragment and the $args that corresponds with its position or number. It returns the first fragment, ‘%s: ‘, unchanged. When it sees ‘%l.’ it replaces the %l directive with a formatted list.

WordPress always tries to make text beautiful. To that end, wp_sprintf_l formats lists with Oxford commas. Two items are “cats and dogs”. Three or more items are “cats, dogs, and birds”. However, if you don’t like Oxford commas you can remove them:

function remove_oxford_commas( $separators ) {
    $separators[ 'between_last_two' ] = ' and ';
    return $separators;
}
add_filter( 'wp_sprintf_l', 'remove_oxford_commas' );

Our list formatter also respects language differences. WordPress translations include wp_sprintf_l()‘s separators so that, for example, the Spanish translation always separates the last two items with ‘ y ‘ with no comma.

You can use <code>wp_sprintf</code> with the ‘%l’ directive anywhere in WordPress since 2.5.0. It’s a lot easier than writing a <code>foreach</code> loop every time.

Something new

Recently a prominent bug crept into some code when the integer argument for %d was wrapped in a call to number_format(). Everything after the first comma was lost. I wished there were a formatting directive to mimic number_format.

While I’m thinking about it, here’s a possibility: ‘%n’. It should automatically localize the thousands separator and decimal point; this alone makes it a compelling upgrade. It should also accept at least one specifier for precision. The other specifiers (sign, padding, alignment, width) would be nice but not necessary.

Image via Wikipedia

p.s. Lisp rocks!

Yesterday I finished reading Conrad Barski’s entertaining Lisp primer, Land of Lisp. He gives only a whiff of Lisp’s format function but I was blown away. It provides tabulation, justification, iteration, recursion, conversion, conditions, and never mind making a cup of coffee, it could run a chain to compete with Starbucks. Here’s a taste:

(format nil
        "~{~a~#[~;, and ~:;, ~]~}"
        (list "Cats" "Dogs" "Birds"))
"Cats, Dogs, and Birds"

I predict that somebody is going to write a theme that allows a lot of new, proprietary themes to be written without the pesky GPL contagion.

Sandbox accomplished that for people who were happy writing CSS and using their own images. They could create a non-GPL skin for Sandbox and nobody would question that. Where Sandbox falls short is in its markup which, though it was thoughtfully written, could never be all things to all people.

So, I expect somebody to write a clever WordPress theme that severs the HTML markup from the WordPress-derived PHP code, properly apply the GPL license to the PHP part, and make a bundle on proprietary skins. You can even call it Severance and I won’t ask for a dime.

(I have been an employee of Automattic since 2005. My employer had no input on this post. However, a salary alone can affect one’s outlook on economic issues.)

<?php
/* modules/capitalP/capitalP.module */
function capitalP_filter($op, $delta = 0, $format = -1, $text = '') {
  switch ( $op ) {
    case 'list' :
      return array(0 => 'capitalP');

    case 'description' :
      return 'Forces the capital "P" in WordPress. To bypass the filter, use quotes: "Wordpress" or \'Wordpress\'.';

    case 'prepare' :
      return $text;

    case 'process' :
      return preg_replace('/(?<!["\'])Wordpress(?!\.?["\'])/', 'WordPress', $text);
 }
}
?>