WordPress, as a content management system, offers a robust framework for building and managing websites. A critical aspect of any successful website is its Search Engine Optimization (SEO), and Yoast SEO is arguably the most popular plugin for achieving this. However, simply installing Yoast SEO isn’t enough. Understanding how it manipulates the document title – the text displayed in browser tabs and search engine results – is crucial for maximizing its effectiveness. This is where the pre_get_document_title filter comes into play. This guide will delve into the intricacies of how Yoast SEO leverages this filter, how to understand its behavior across different WordPress versions, and how developers can extend or modify this functionality. We will explore the underlying mechanisms, providing a detailed understanding for WordPress developers and SEO professionals alike.
The Evolution of Title Handling in WordPress
The way WordPress generates and manages document titles has evolved over time, particularly with the introduction of the pre_get_document_title filter in WordPress version 4.4. Before this version, the wp_title hook was the primary method for modifying the title. However, wp_title was often problematic due to its late execution in the page rendering process and potential conflicts with themes and other plugins. The introduction of pre_get_document_title provided a more reliable and earlier point for intervention, allowing developers to modify the title before it was finalized.
Yoast SEO was quick to adopt this new filter, utilizing it to generate and control the SEO title. The plugin now employs both pre_get_document_title and wp_title, but their roles differ significantly depending on the WordPress version. In versions 4.4 and later, pre_get_document_title takes precedence, generating the SEO title. wp_title still fires, but Yoast SEO’s code ensures it doesn’t override the title already set by pre_get_document_title. For older versions, wp_title remains the primary mechanism. This dual approach ensures backward compatibility while leveraging the benefits of the newer filter when available.
Understanding the pre_get_document_title Filter
The pre_get_document_title filter is a powerful tool for modifying the document title before it's generated by WordPress. It allows developers to intercept the title generation process and apply custom logic to alter the title based on various factors, such as the post type, category, or user role.
Here's a basic example of how to use the filter:
php
add_filter('pre_get_document_title', 'your_custom_function');
function your_custom_function($title) {
// Your custom code here
return $title;
}
This code snippet registers a function your_custom_function to be executed when the pre_get_document_title filter is triggered. The function receives the current title as an argument and must return the modified title. The flexibility of this filter allows for a wide range of customizations, from adding prefixes or suffixes to the title to completely rewriting it based on specific conditions.
How Yoast SEO Utilizes pre_get_document_title
Yoast SEO’s implementation of pre_get_document_title is central to its title optimization features. The plugin stores the SEO title for each post or page in the wp_postmeta table under the _yoast_wpseo_title key. This title is often constructed using variables like %%title%%, %%page%%, %%sep%%, and %%sitename%%, allowing for dynamic title generation.
The plugin’s WPSEO_Frontend::title() method checks if the $title property is already set. If it is, the existing title is returned. Otherwise, the title is generated using the WPSEO_Frontend::generate_title() method. This ensures that the SEO title is consistently applied across the website.
Here's a breakdown of the common Yoast SEO title variables:
| Variable | Description |
|---|---|
%%title%% |
The title of the current post or page. |
%%page%% |
The page number for paginated posts. |
%%sep%% |
The separator between the title and site name. |
%%sitename%%| The name of the website. |
|
%%category%%| The category of the current post. |
These variables provide a powerful way to create dynamic and SEO-friendly titles that adapt to the content of each page.
Retrieving Yoast SEO Title Information
Developers often need to access the Yoast SEO title information programmatically. Here are two functions to achieve this:
1. Getting the Post/Page Default Title:
php
function yoastVariableToTitle($post_id) {
$yoast_title = get_post_meta($post_id, '_yoast_wpseo_title', true);
$title = strstr($yoast_title, '%%', true);
if (empty($title)) {
$title = get_the_title($post_id);
}
return $title;
}
This function extracts the portion of the Yoast SEO title before the first %% variable. This is useful for retrieving the custom title entered by the administrator, if any.
2. Getting the Full Meta Title:
php
function yoastVariableToTitle($post_id) {
$yoast_title = get_post_meta($post_id, '_yoast_wpseo_title', true);
$title = strstr($yoast_title, '%%', true);
if (empty($title)) {
$title = get_the_title($post_id);
}
$wpseo_titles = get_option('wpseo_titles');
$sep_options = WPSEO_Option_Titles::get_instance()->get_separator_options();
if (isset($wpseo_titles['separator']) && isset($sep_options[$wpseo_titles['separator']])) {
$sep = $sep_options[$wpseo_titles['separator']];
} else {
$sep = '-'; //setting default separator if Admin didn't set it from backed
}
$site_title = get_bloginfo('name');
$meta_title = $title . ' ' . $sep . ' ' . $site_title;
return $meta_title;
}
This function retrieves the complete meta title, including the custom title, separator, and site name, as configured in Yoast SEO.
Modifying the Yoast SEO Title
While Yoast SEO provides extensive control over the title, there may be situations where you need to modify it further. To do this, you should hook into the wp_title filter after Yoast SEO has applied its changes (priority 20 or higher).
php
add_filter( 'wp_title', 'wpse_258323_title', 20, 2 );
function wpse_258323_title( $title, $post_id ) {
// Do something with the $title
return $title;
}
This code snippet demonstrates how to hook into the wp_title filter and modify the title after Yoast SEO has generated it. The priority of 20 ensures that your function is executed after Yoast SEO’s function, allowing you to override or extend its changes.
WordPress Version Compatibility
As previously mentioned, the behavior of pre_get_document_title and wp_title differs depending on the WordPress version. Here's a quick reference table:
| WordPress Version | pre_get_document_title |
wp_title |
|---|---|---|
| < 4.4 | Not Available | Primary |
| >= 4.4 | Primary | Secondary |
Developers must consider these differences when writing code that interacts with the title generation process. Using conditional logic to detect the WordPress version and adjust the code accordingly is often necessary to ensure compatibility across different environments.
Key Terminology
- Filter Hook: A mechanism in WordPress that allows developers to modify data before it's processed.
pre_get_document_title: A filter hook specifically for modifying the document title before it's generated.wp_title: A filter hook for modifying the document title, historically the primary method beforepre_get_document_title.wp_postmeta: A WordPress database table used to store post-specific metadata, including Yoast SEO title information.- SEO Title: The title used for search engine optimization purposes, often different from the displayed page title.
The Bottom Line
Mastering the interplay between Yoast SEO, the pre_get_document_title filter, and WordPress version compatibility is essential for achieving optimal SEO results. By understanding how these components work together, developers and SEO professionals can create dynamic, SEO-friendly titles that improve search engine rankings and drive traffic to their websites. The pre_get_document_title filter provides a powerful and flexible way to customize the title generation process, allowing for a wide range of modifications and extensions. Staying informed about the latest WordPress updates and Yoast SEO features is crucial for maintaining a well-optimized website.