Using Custom Rewrite Rules To Control Urls In Wordpress

Why URL Control Matters

Controlling URLs is crucial for any WordPress website. Custom rewrite rules allow site owners granular control over URLs to improve user experience, aid search engine optimization, and customize site behavior.

Improves User Experience

Clean, descriptive, and consistent URLs positively impact user experience. Rewrite rules can create human-readable URLs that clearly communicate page content. For example, a dynamic URL like /?product=blue-socks could instead show as /blue-socks. Users understand what a page is about faster.

Aids Search Engine Optimization

Search engines factor URL structure into rankings. Custom URLs containing relevant keywords can improve visibility in search results. Rewrite rules also allow site owners to change URLs without breaking external links which helps search engine rankings.

Allows Customization of Site Behavior

Beyond aesthetics, rewrite rules can alter how WordPress handles requests. URL parts can be used as variables to load custom page templates and content. For advanced sites, rules provide extensive control over routing and redirects.

Basic Principles of Rewrite Rules

Learning foundational concepts helps utilize the full power of WordPress rewrite capabilities.

How WordPress Handles Requests

When a visitor requests a page, WordPress maps the URL to associated content. Requests are handled in this order:

Permalinks
Redirects
Rewrite rules

So permalinks convert URLs to query variables first. Rewrite rules process next and run before redirects. Understanding order of operations is key to effective rules.

Understanding Rewrite Tags and Matching Patterns

Rewrite rules target URLs using regular expressions then output substitutions. They are defined using these parts:

Match – Target URL pattern to rewrite
Substitution – Replacement output
Tags – Variables accessible in substitution

For example, this excerpt matches a URL and passes the product name to the rewrite:

'product/([a-z]+)/' => 'index.php?product=$matches[1]'

Tags allow rules to dynamically insert matched content into substitutions with $matches[1], $matches[2] etc. This exposes lots of possibilities.

Redirects vs Direct Rewrites

Rules can output redirects or direct rewrites:

A redirect transfers the browser to a new URL.
A direct rewrite maps the URL to content internally without visibly changing the URL in the browser.

So direct rewrites maintain the same URL while redirects visibly change it. Each approach serves different purposes.

Creating Custom Rewrite Rules

With core concepts covered, custom rewrite rules can now be created to fit project needs…

Adding Rules to functions.php

The functions.php file is where rewrite rules are added in WordPress. To enqueue a rule, hook into the ‘generate_rewrite_rules’ filter:

add_filter('generate_rewrite_rules', 'custom_rewrite_rules');
function custom_rewrite_rules($rules) {
  // Add rules here...
  return $rules;
}

Then flush the permalinks structure after adding rules to the database.

Conditional Rules and Regular Expressions

Rules can run conditionally when regular expression matching groups are used. For example, this rule redirects iPhone users to the mobile site:

 
'^(.*)(iPad|iPhone|Android)(.*)$' => 'http://m.example.com$1$3'

The parentheses capture matching text to $1 and $3 as variables in the substitution URL.

Examples

Redirecting a Single URL

This rule permanently redirects requests from an old URL to a new location:

'/old-page.html' => 'http://example.com/new-page/'

Rewriting a Category to Act Like a Tag

This allows category URLs to work like tag URLs for custom navigation:

'category/(.+)' => 'tag/$matches[1]'

Troubleshooting Rewrite Rules

Debugging rules can be challenging. These techniques identify and fix problems.

Debugging with Rewrite Logging

Enable rewrite debugging in wp-config.php:

define('WP_DEBUG_LOG', true);

Failed rules then output to debug.log. Review entries to pinpoint issues.

Common Problems and Solutions

Here are some common rewrite problems and potential fixes:

Rule Totally Fails – Flush permalinks and test with a basic rule like rerouting index to about. Typos are common culprits.
Rule Partially Fails – Use $matches to double check if parts of match pattern are empty. Target more specific URLs in regex.
Rewrite Loops – Order matters, put redirects above direct rewrites to avoid loops.

Testing Rules Without Affecting Site

Test rules locally or on staging versions before going live. Plugins like Rewrite Rules Inspector add a custom endpoint for testing too.

Additional Tips and Tricks

Further extend the power of WordPress rewriting.

Rewrite Rule Code Samples for Reference

Use these snippets as basic templates for common needs:

Redirect HTTP to HTTPS:

 
'^(.*)//?example.com(/[^\?]*)(\?.*)?$' => 'https\://example.com$2$3'

Redirect a Subdirectory:

'^books/(.*)$' => '/library/$1'

Plugins that Extend Rewrite Functionality

Plugins provide added rewrite management and tools:

Redirection – Redirect manager UI with regex assistant
String Locator – Improves handling of static URLs

Caching Considerations

New rules may require clearing server and plugin caches. Also consider caching needs upfront when crafting extensive logic.

Using Custom Rewrite Rules To Control Urls In WordPress