Core Competency

Alex King · alexking.org

Original contributor to WordPress core
Hosted first theme competitions for WordPress (2004, 2005)
Released dozens of plugins/themes
Architect of Carrington Core,
Carrington Build & RAMP
Founder of Crowd Favorite

`the_content()`

is “Special”

wp_posts table in database

global $post in templates

Database columns → Object properties

Data

$post->ID

Return

get_the_ID()

Echo

the_ID()

Data

$post->post_title

Return

get_the_title()

apply_filters('the_title' …

Echo

the_title()

Data

?

Return

get_the_content()

apply_filters('the_content' …

Echo

the_content()

Developers love patterns.

Developers assume consistency.

the_content()

NEVER references

$post->post_content

The data does come from

$post->post_content

just not like you might expect.

Let's follow the rabbit hole…

1 of 1

`the_content()`

wp-includes/post-template.php, line 164

function the_content($more_link_text = null, $stripteaser = false) {
	$content = get_the_content($more_link_text, $stripteaser);
	$content = apply_filters('the_content', $content);
	$content = str_replace(']]>', ']]>', $content);
	echo $content;
}

`get_the_content()`

wp-includes/post-template.php, line 180

function get_the_content($more_link_text = null, $stripteaser = false) {
	global $post, $more, $page, $pages, $multipage, $preview;

	if ( null === $more_link_text )
		$more_link_text = __( '(more...)' );

	$output = '';
	$hasTeaser = false;

	// If post password required and it doesn't match the cookie.
	if ( post_password_required($post) )
		return get_the_password_form();

	if ( $page > count($pages) ) // if the requested page doesn't exist
		$page = count($pages); // give them the highest numbered page that DOES exist

	$content = $pages[$page-1];

	if ( preg_match('//', $content, $matches) ) {
		$content = explode($matches[0], $content, 2);
		if ( !empty($matches[1]) && !empty($more_link_text) )
			$more_link_text = strip_tags(wp_kses_no_null(trim($matches[1])));

		$hasTeaser = true;
	} else {
		$content = array($content);
	}
	if ( (false !== strpos($post->post_content, '') && ((!$multipage) || ($page==1))) )
		$stripteaser = true;
	$teaser = $content[0];
	if ( $more && $stripteaser && $hasTeaser )
		$teaser = '';
	$output .= $teaser;
	if ( count($content) > 1 ) {
		if ( $more ) {
			$output .= '' . $content[1];
		} else {
			if ( ! empty($more_link_text) )
				$output .= apply_filters( 'the_content_more_link', ' ID}\" class=\"more-link\">$more_link_text", $more_link_text );
			$output = force_balance_tags($output);
		}
	}

	if ( $preview ) // preview fix for javascript bug with foreign languages
		$output =	preg_replace_callback('/\%u([0-9A-F]{4})/', '_convert_urlencoded_to_entities', $output);

	return $output;
}

So get_the_content() returns $output

Which was created from $content

Which was pulled from global $pages

1 of 7

Where is global $pages set?

You'll recognize this...

while ( have_posts() ) : the_post();
// ...
endwhile;

The loop...

while ( have_posts() ) : the_post();
// ...
endwhile;

`the_post()`

wp-includes/query.php, line 784

function the_post() {
	global $wp_query;

	$wp_query->the_post();
}

`$wp_query->the_post()`

wp-includes/query.php, line 2815


class WP_Query {

// ...

	function the_post() {
		global $post;
		$this->in_the_loop = true;

		if ( $this->current_post == -1 ) // loop has just started
			do_action_ref_array('loop_start', array(&$this));

		$post = $this->next_post();
		setup_postdata($post);
	}

`setup_postdata()`

wp-includes/query.php, line 3589

function setup_postdata($post) {
	global $id, $authordata, $currentday, $currentmonth, $page, $pages, $multipage, $more, $numpages;

	$id = (int) $post->ID;

	$authordata = get_userdata($post->post_author);

	$currentday = mysql2date('d.m.y', $post->post_date, false);
	$currentmonth = mysql2date('m', $post->post_date, false);
	$numpages = 1;
	$page = get_query_var('page');
	if ( !$page )
		$page = 1;
	if ( is_single() || is_page() || is_feed() )
		$more = 1;
	$content = $post->post_content;
	if ( strpos( $content, '' ) ) {

		if ( $page > 1 )
			$more = 1;
		$multipage = 1;
		$content = str_replace("\n\n", '', $content);
		$content = str_replace("\n", '', $content);
		$content = str_replace("\n", '', $content);
		$pages = explode('', $content);
		$numpages = count($pages);
	} else {
		$pages = array( $post->post_content );
		$multipage = 0;
	}

	do_action_ref_array('the_post', array(&$post));

	return true;
}

the_content()

get_the_content()

global $pages

the_post()

$wp_query->the_post()

setup_postdata()

$post->post_content

Why does
this matter?

Documentation tells you what the code is supposed to do.
Reading the code tells what it does.
Understanding the code let's you choose the right tool for the job.

Examples

1 of 7

the_content filter is commonly used to prepend and append features to posts/pages.

page 1 and page 2 example

`WP_Query, get_posts()`

wp-includes/query.php, line 2756

if ( !$q['suppress_filters'] )
	$this->posts = apply_filters_ref_array('the_posts', array( $this->posts, &$this ) );

$this->post_count = count($this->posts);

// Always sanitize
foreach ( $this->posts as $i => $post ) {
	$this->posts[$i] = sanitize_post( $post, 'raw' );
}

if ( $q['cache_results'] )
	update_post_caches($this->posts, $post_type, $q['update_post_term_cache'], $q['update_post_meta_cache']);

if ( $this->post_count > 0 ) {
	$this->post = $this->posts[0];
}

return $this->posts;

function my_content_first($posts, $query) {
	foreach ($posts as &$post) {
		$post->post_content = '<div class="banner">FIRST!</div>'
			.$post->post_content;
	}
	return $posts;
}
add_filter('the_posts', 'my_content_first', 10, 2);

`the_excerpt()`

Can be set manually.
Auto-generated from
$post->post_content
Truncates by words (default 55), not by characters.

`wp_trim_excerpt()`

wp-includes/formatting.php, line 2111

function wp_trim_excerpt($text = '') {
	$raw_excerpt = $text;
	if ( '' == $text ) {
		$text = get_the_content('');

		$text = strip_shortcodes( $text );

		$text = apply_filters('the_content', $text);
		$text = str_replace(']]>', ']]>', $text);
		$excerpt_length = apply_filters('excerpt_length', 55);
		$excerpt_more = apply_filters('excerpt_more', ' ' . '[...]');
		$text = wp_trim_words( $text, $excerpt_length, $excerpt_more );
	}
	return apply_filters('wp_trim_excerpt', $text, $raw_excerpt);
}

1 of 1

What do you think happens if you put something like this at the beginning of a post?

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29yZGluYXRlcyI6bnVsbCwicmV0d2VldF9jb3VudCI6MCwiaWRfc3RyIjoiMTk1NDIzODc4NzI0NTk5ODA5IiwiaW5f
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ykgdG9uaWdodC4gI3dvcmRwcmVzcyJ9";s:4:"urls";a:2:{i:0;s:41:"http://alexking.org/blog/2012/04
/26/13316";i:1;s:28:"http://alexking.org/?p=13316";}s:7:"account";O:8:"stdClass":1:{s:4:"us
er";O:8:"stdClass":39:{s:20:"contributors_enabled";s:0:"";s:14:"statuses_count";s:4:"3676";
s:13:"notifications";s:0:"";s:18:"profile_link_color";s:6:"0000FF";s:9:"protected";s:0:"";s
:23:"profile_image_url_https";s:66:"https://si0.twimg.com/profile_images/17084282/alex_king
_normal.jpg";s:16:"favourites_count";s:3:"877";s:28:"profile_sidebar_border_color";s:6:"556
699";s:15:"followers_count";s:4:"4380";s:4:"name";s:9:"Alex King";s:12:"listed_count";s:3:"
398";s:9:"time_zone";s:27:"Mountain Time (US & Canada)";s:8:"verified";s:0:"";s:28:"pr
ofile_use_background_image";s:0:"";s:10:"utc_offset";s:6:"-25200";s:17:"profile_image_url";
s:64:"http://a1.twimg.com/profile_images/17084282/alex_king_normal.jpg";s:11:"description"
;s:44:"Web developer and founder of Crowd Favorite.";s:24:"profile_background_color";s:6:"8
899cc";s:4:"lang";s:2:"en";s:28:"profile_background_image_url";s:47:"http://a0.twimg.com/im
ages/themes/theme1/bg.png";s:11:"screen_name";s:11:"alexkingorg";s:6:"status";O:8:"stdClass
":18:{s:19:"in_reply_to_user_id";s:0:"";s:9:"truncated";s:0:"";s:21:"in_reply_to_status_id"
;s:0:"";s:9:"favorited";s:0:"";s:25:"in_reply_to_status_id_str";s:0:"";s:5:"place";s:0:"";s
:3:"geo";s:0:"";s:11:"coordinates";s:0:"";s:23:"in_reply_to_screen_name";s:0:"";s:23:"in_re
ply_to_user_id_str";s:0:"";s:6:"source";s:101:"Twitter for Mac";s:6:"id_str";s:18:"1013087
[...]

Easy solution via filter.

function excerpt_sanity($excerpt) {
	if (strlen($excerpt) > 550) {

// take care of it.

	}
	return $excerpt;
}
add_filter('get_the_excerpt', 'excerpt_sanity', 50);

Slashes

1. Validation / Sanitization

2. (stuff)

3. Encoding / Escaping

Push $_POST directly into functions that save.

WordPress forces slashes on $_POST data
wp_magic_quotes() defined wp-includes/load.php, line 531
called in wp-settings.php, line 218
stripslashes_deep()
add_magic_quotes()

1 of 1

You may have seen this in plugins/themes, etc.

update_post_meta($post->ID, '_my_meta_key', $_POST['_my_meta_key']);

`update_metadata()`

wp-includes/meta.php, line 101

function update_metadata($meta_type, $object_id, $meta_key, $meta_value, $prev_value = '') {

// [...]

	// expected_slashed ($meta_key)
	$meta_key = stripslashes($meta_key);
	$passed_value = $meta_value;
	$meta_value = stripslashes_deep($meta_value);
	$meta_value = sanitize_meta( $meta_key, $meta_value, $meta_type );

// [...]

}

1. Make API call to Twitter, Facebook, etc.

2. Store data in post meta.

$my_api_data = get_twitter_data();
update_post_meta($post->ID, '_my_meta_key', $my_api_data);

Stripping slashes on JSON data is problematic.

// before
{"profile_image_url":"http:\/\/a0.twimg.com\/profile_images\/17084282\/alex_king_normal.jpg"}

// after
{"profile_image_url":"http://a0.twimg.com/profile_images/17084282/alex_king_normal.jpg"}

We're gonna need more slashes.

$my_api_data = get_twitter_data();
update_post_meta($post->ID, '_my_meta_key', add_magic_quotes($my_api_data));

1 of 1

`wp_insert_post()`

wp-includes/post.php, line 2460

function wp_insert_post($postarr, $wp_error = false) {

// [...]

	// expected_slashed (everything!)
	$data = compact( array( 'post_author', 'post_date', 'post_date_gmt', 'post_content',
		'post_content_filtered', 'post_title', 'post_excerpt', 'post_status', [...] ) );
	$data = apply_filters('wp_insert_post_data', $data, $postarr);
	$data = stripslashes_deep( $data );

// [...]

}

$post_data = array(
	'post_status' => 'publish',
	'post_type' => 'post',
	'post_title' => 'This is my title',
	'post_content' => 'Crazy with the backslashes \\\\\\\\',
);

// wrong

wp_insert_post($post_data);

// right (as of WP 3.4.1)

wp_insert_post(add_magic_quotes($post_data));

`wp_insert_user()`

wp-includes/user.php, line 1251

function wp_insert_user($userdata) {

// [...]

	$data = compact( 'user_pass', 'user_email', 'user_url', 'user_nicename', 'display_name',
		'user_registered' );
	$data = stripslashes_deep( $data );

// [...]

}

Working on a patch for WordPress 3.5

(Core ticket #21767 — it's a big change)

JavaScript
Debugging

Add this to your wp-config.php file.

define('SCRIPT_DEBUG', true);

Database Queries

Most common performance bottleneck
Easiest way to improve page
generation time
Every database query should be intentional

1 of 1

Get the two most recent posts.

$example = new WP_Query(array(
	'posts_per_page' => 2,
	'orderby' => 'date',
	'order' => 'DESC',
));

This actually generates five database queries.

Query #1: find IDs of posts matching query args

SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts
WHERE 1=1
AND wp_posts.post_type = 'post'
AND (
	wp_posts.post_status = 'publish'
	OR wp_posts.post_status = 'future'
	OR wp_posts.post_status = 'draft'
	OR wp_posts.post_status = 'pending'
	OR wp_posts.post_status = 'private'
)
ORDER BY wp_posts.post_date DESC
LIMIT 0, 2

Query #2: check total number of results

SELECT FOUND_ROWS()

Query #3: get full post data

SELECT wp_posts.*
FROM wp_posts
WHERE ID IN (10134,10263)

Query #4: find taxonomy terms for selected posts

SELECT t.*, tt.*, tr.object_id
FROM wp_terms AS t
INNER JOIN wp_term_taxonomy AS tt
	ON tt.term_id = t.term_id
INNER JOIN wp_term_relationships AS tr
	ON tr.term_taxonomy_id = tt.term_taxonomy_id
WHERE tt.taxonomy IN ('category', 'post_tag', 'post_format')
AND tr.object_id IN (10134, 10263)
ORDER BY t.name ASC

Query #5: find postmeta for selected posts

SELECT post_id, meta_key, meta_value
FROM wp_postmeta
WHERE post_id IN (10134,10263)

1 of 1

Get the two most recent posts in a category.

$example = new WP_Query(array(
	'category_name' => 'uncategorized',
	'posts_per_page' => 2,
	'orderby' => 'date',
	'order' => 'DESC',
));

This actually generates eight database queries.

Query #1: find term ID

SELECT wp_term_taxonomy.term_id
FROM wp_term_taxonomy
INNER JOIN wp_terms USING (term_id)
WHERE taxonomy = 'category'
AND wp_terms.slug IN ('uncategorized')

Query #2: find term taxonomy ID

SELECT term_taxonomy_id
FROM wp_term_taxonomy
WHERE taxonomy = 'category'
AND term_id IN (1)

Query #3: get detailed term info

SELECT t.*, tt.*
FROM wp_terms AS t
INNER JOIN wp_term_taxonomy AS tt
	ON t.term_id = tt.term_id
WHERE tt.taxonomy = 'category'
AND t.slug = 'uncategorized'
LIMIT 1

Query #4: find post IDs that match query

SELECT SQL_CALC_FOUND_ROWS wp_posts.ID
FROM wp_posts
INNER JOIN wp_term_relationships
	ON (wp_posts.ID = wp_term_relationships.object_id)
WHERE 1=1
AND ( wp_term_relationships.term_taxonomy_id IN (1) )
AND wp_posts.post_type = 'post'
AND (
	wp_posts.post_status = 'publish'
	OR wp_posts.post_status = 'future'
	OR wp_posts.post_status = 'draft'
	OR wp_posts.post_status = 'pending'
	OR wp_posts.post_status = 'private'
)
GROUP BY wp_posts.ID
ORDER BY wp_posts.post_date DESC
LIMIT 0, 2

Query #5: check total number of results

SELECT FOUND_ROWS()

Query #6: get full post data

SELECT wp_posts.*
FROM wp_posts
WHERE ID IN (10134,10263)

Query #7: find taxonomy terms for selected posts

SELECT t.*, tt.*, tr.object_id
FROM wp_terms AS t
INNER JOIN wp_term_taxonomy AS tt
	ON tt.term_id = t.term_id
INNER JOIN wp_term_relationships AS tr
	ON tr.term_taxonomy_id = tt.term_taxonomy_id
WHERE tt.taxonomy IN ('category', 'post_tag', 'post_format')
AND tr.object_id IN (10134, 10263)
ORDER BY t.name ASC

Query #8: find postmeta for selected posts

SELECT post_id, meta_key, meta_value
FROM wp_postmeta
WHERE post_id IN (10134,10263)

Put WP_Query on a diet.

$example = new WP_Query(array(
	'posts_per_page' => 2,
	'orderby' => 'date',
	'order' => 'DESC',
	'no_found_rows' => true,
	'update_post_term_cache' => false,
	'update_post_meta_cache' => false,
));

Brings it down to two queries.

`get_post()`

wp-includes/post.php, line 380

function &get_post(&$post, $output = OBJECT, $filter = 'raw') {
// [...]
	if ( ! $_post = wp_cache_get($post_id, 'posts') ) {
		$_post = $wpdb->get_row($wpdb->prepare("
			SELECT * FROM $wpdb->posts
			WHERE ID = %d LIMIT 1
		", $post_id));
		if ( ! $_post )
			return $null;
		_get_post_ancestors($_post);
		$_post = sanitize_post($_post, 'raw');
		wp_cache_add($_post->ID, $_post, 'posts');
	}
// [...]
}

Context matters.

1 of 1

Tools

Roll your own

define('SAVE_QUERIES', true);

global $wpdb;
print_r($wpdb->queries);

Debug Bar — http://wordpress.org/extend/plugins/debug-bar/

debug bar

Bonus tip: `is_main_query()`

wp-includes/query.php

// line 724
function is_main_query() {
	global $wp_query;
	return $wp_query->is_main_query();
}

// line 3514
class WP_Query {
	function is_main_query() {
		global $wp_the_query;
		return $wp_the_query === $this;
	}
}

Post Meta vs.
Taxonomies

Both can be used to set attributes on a post/page/custom post type.
Relatively easy to present a custom UI for both (in the admin).
Context matters.

Use a taxonomy when you need to query by the attribute.
Use post meta when you don't.

Menus

<php wp_nav_menu( array( 'theme_location' => 'primary' ) ); ?>

wp_options
wp_posts
wp_postmeta
wp_terms
wp_term_relationships
wp_term_taxonomy

`wp_options`

Maps menus to theme locations
Mapping is stored on a per-theme basis
theme_mods_(theme slug)

`wp_posts` & `wp_postmeta`

Menu items
Type of item, details about it
_menu_item_type, _menu_item_menu_item_parent, _menu_item_object_id, _menu_item_object, _menu_item_target, _menu_item_classes, _menu_item_xfn, _menu_item_url

`wp_terms`,
`wp_term_taxonomy` &
`wp_term_relationships`

wp_terms holds the menu name
wp_term_taxonomy stores the registration of the nav_menu taxonomy
wp_term_relationships attaches the menu items to the menu term

Delete Post

1 of 1

`wp_delete_post()`

wp-includes/post.php, line 2022

function wp_delete_post( $postid = 0, $force_delete = false ) {

// [...]

	do_action('before_delete_post', $postid);

// [...]

	wp_delete_object_term_relationships($postid, get_object_taxonomies($post->post_type));

// [...]

	$comment_ids = $wpdb->get_col( $wpdb->prepare( "SELECT comment_ID FROM $wpdb->comments WHERE comment_post_ID = %d", $postid ));
	foreach ( $comment_ids as $comment_id )
		wp_delete_comment( $comment_id, true );

	$post_meta_ids = $wpdb->get_col( $wpdb->prepare( "SELECT meta_id FROM $wpdb->postmeta WHERE post_id = %d ", $postid ));
	foreach ( $post_meta_ids as $mid )
		delete_metadata_by_mid( 'post', $mid );

	do_action( 'delete_post', $postid );

	do_action( 'delete_post', $postid );
	$wpdb->delete( $wpdb->posts, array( 'ID' => $postid ) );
	do_action( 'deleted_post', $postid );

// [...]

	do_action('after_delete_post', $postid);

	return $post;
}

Post GUID

Globally unique identifier

http://en.wikipedia.org/wiki/Globally_unique_identifier

Page GUIDs were not unique prior to WordPress 3.1

They were all the site URL: http://example.com/

Trac ticket #15041

This data has not been "cleaned up" yet

Trac ticket #18286

Plugin to fix it: https://github.com/crowdfavorite/wp-guid-fix

$my_guid = $service_name.'-'.$service_item_id;
// 'twitter-256996758964563968'

wp_insert_post(array(
	'post_title' => $my_title,
	'post_content' => $my_content,
	'guid' => $my_guid
));

The GUID must begin with http://

$my_guid = 'http://'.$service_name.'-'.$service_item_id;
// 'http://twitter-256996758964563968'

wp_insert_post(array(
	'post_title' => $my_title,
	'post_content' => $my_content,
	'guid' => $my_guid
));

Security

Always upgrade immediately.

Connect

alexking.org | @alexkingorg
crowdfavorite.com | @crowdfavorite

Slides

alexking.org/speaking
Built with the excellent Impress.js
code: github.com/alexkingorg/core-competency
Slide styling by Jared Cornwall (@jaredkc)
Code examples are from WordPress 3.4.1

Core Competency

the_content()

the_content()

get_the_content()

You'll recognize this...

The loop...

the_post()

$wp_query->the_post()

setup_postdata()

Why does this matter?

Examples

WP_Query, get_posts()

the_excerpt()

wp_trim_excerpt()

Slashes

update_metadata()

wp_insert_post()

wp_insert_user()

JavaScriptDebugging

Database Queries

get_post()

Tools

Bonus tip: is_main_query()

Post Meta vs.Taxonomies

Menus

wp_options

wp_posts & wp_postmeta

wp_terms, wp_term_taxonomy & wp_term_relationships

Delete Post

wp_delete_post()

Post GUID

Security

`the_content()`

`the_content()`

`get_the_content()`

`the_post()`

`$wp_query->the_post()`

`setup_postdata()`

Why does
this matter?

`WP_Query, get_posts()`

`the_excerpt()`

`wp_trim_excerpt()`

`update_metadata()`

`wp_insert_post()`

`wp_insert_user()`

JavaScript
Debugging

`get_post()`

Bonus tip: `is_main_query()`

Post Meta vs.
Taxonomies

`wp_options`

`wp_posts` & `wp_postmeta`

`wp_terms`,
`wp_term_taxonomy` &
`wp_term_relationships`

`wp_delete_post()`