What Are Permalinks? What is URL Rewriting?<\/h2>\n
URLs are the vehicle used to send HTTP GET requests over the web. More precisely, the GET method submits Take the following URL:<\/p>\n http:\/\/example.com\/?p=123<\/em><\/p>\n The question mark splits this URL into two parts. The first part is the domain name, the second part is the query string, which is a set of query variables and values determining the resource requested by the user. The query string identifies the resource, but it doesn’t tell us anything about its contents. We can say that it’s not semantically meaningful for humans and machines.<\/p>\n Thanks to the Rewrite API, we can translate non-semantic URLs into their semantic equivalent<\/a> with an operation of URL rewriting. A rewrite rule would translate the preceding URL into the following structure:<\/p>\n http:\/\/example.com\/category\/post-title\/<\/em><\/p>\n With the category and post title within the URL, this structure describes more precisely the resource content for both humans and search engines, resulting in a usable, accessible and SEO-friendly URL. It can be bookmarked, shared and stored in a number of ways and it should never change in the long term so that the linked resource could be permanently targeted. This is the reason we call them permalinks.<\/p>\n We can ask WordPress to retrieve almost anything from a site’s database. Generally, you query for posts in a specified category, or labeled with a precise tag, or published during a specific period of time. When the user submits a URL, WordPress automatically handles the request and, according to the template hierarchy<\/a> rules, shows the results in a single page or within an archive.<\/p>\n In the first part of this post,\u00a0I’ll show you how to make use of built-in query string variables and how to register our own custom variables, we’ll instruct WordPress to get these variables from the URLs and use them to query the database, and then we will output the resulting list of posts into a custom archive page.<\/p>\n In the last part of this post, I’ll show you the tools WordPress provides us to translate these semantically unintelligible query strings into meaningful, accessible, usable and SEO-optimized permalinks. I’ll also give you an overview of default and custom permalink structures provided by WordPress, and finally we’ll build custom pretty permalinks using the Rewrite API.<\/p>\n Query vars are the keys that define any SQL query WordPress runs against the database. These variables come in two main categories, depending on the way we can use them. Private query vars<\/strong> can be only set within a script, while public query vars<\/strong> can be sent to WordPress with a query string.<\/p>\n Besides public and private variables, WordPress allows us to register our own custom query vars<\/strong>.<\/p>\n In a URL, public query variables are the keys following the question mark (the query string), and are visible when we’ve not enabled Pretty permalinks on the\u00a0Settings \u2192 Permalinks<\/a> admin page. The following URL is an example:<\/p>\n example.com\/?author_name=carlodaniele<\/em><\/p>\n example.com\/?author_name=carlodaniele&tag=toolbar<\/em><\/p>\n Now, WordPress will get all posts by example.com\/?post_type=food&food-family=greens<\/em><\/p>\n Unlike public variables, private query vars can be only used within a script. For this reason, I won’t explore them in this post (you can read more in the WordPress Codex<\/a>). Here, I will simply point out that the following URL won’t give us the expected result:<\/p>\n example.com\/?author__in=2,4,6 <\/em><\/p>\n Here Most\u00a0times, thanks to public query vars, we don’t need to write code to manage a\u00a0user’s requests, we just need to build the right query strings and WordPress will do the rest.<\/p>\n Now, have a look at the following list of public vars:<\/p>\nkey=value<\/code> pairs within a URL to get a response from a specified resource (read more about this topic at\u00a0W3Schools<\/a>).<\/p>\nURLs in WordPress: Query Vars and Query Strings<\/h2>\n
Public and Private Query Vars<\/h2>\n
author_name<\/code> is a public query var telling WordPress that the user is looking for all posts by the user\u00a0carlodaniele<\/code>. We can add a number of public query vars to the query string, as we do in the following URL:<\/p>\ncarlodaniele<\/code> and tagged as toolbar<\/code>. And we can do even more. The next query string is a combination of a custom post type and a taxonomy-name=taxonomy-term<\/em> pair.<\/p>\nauthor__in<\/code> is a private query var, and WordPress won’t show the posts by the specified authors.<\/p>\n
![\"Custom](\"https:\/\/wpmudev.com\/blog\/wp-content\/uploads\/2016\/03\/custom_structure.png\")
![\"Query](\"https:\/\/wpmudev.com\/blog\/wp-content\/uploads\/2016\/03\/query_monitor.png\")