Need help setting canonical within PHP

Question

First, I want to preface that I am not very good with php so I am looking for some guidance. I'm working on a website using Dreamweaver that is being accessed through .davaccess

each php page has the following variables:

<?php
require_once "../config.php";
$title="Custom Title I enter";
$metaDescription="Custom Description I enter.";        
include_once (INCLUDES_PATH  . "/header.php");
?>  

And the header.php includes this section:

<title><?php echo $title; ?></title>
<meta name="description" content="<?php echo $metaDescription ?>" />
<base href="<?php echo $config['urls']['baseUrl'] ?>">

My thought is that I need to add something in the header file so I can add my own URL on the individual pages. Based on how the title and description have worked, I tried including the following:

<link rel="canonical" href="<?php echo $canonical ?>" />

but that ends up just making each page canonicalize to the base URL, before I add anything to individual pages.

What I'm looking for is a way to add some code that can autopopulate the current URL as the canonical, and possibly update it on individual pages if necessary. Any help would be greatly appreciated. Thank you

Answer 1

What I do for pages that I want to mark as canonical is put the following code in my header.php file that is loaded on each page:
<link rel='canonical' href='<?php echo 'https://' . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI']; ?>'>

This loads the prefix https:// plus the domain www.example.com plus the page page.php resulting in
<link rel='canonical' href='https://www.example.com/page.php'>

Answer 2

You can set your canonical to be the current page URL. According to Get the full URL in PHP on stackoverflow.com, you just need to initiate your $canonical variable like:

$canonical = (isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] === 'on' ? "https" : "http") . "://" . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'];

Maybe right where your $title is set would also be a good place to do that.

---

However, the better way to set the canonical is by computing it. You don't say how your URLs are structured, so I will give you an example from this site. Lets say your URL is /questions/125939/need-help-setting-canonical-within-php.

Your rewrite rules might modify that to /show-question.php?question-id=125939.

Pseudocode for computing the URL might look like:

questionId = getCgiVar('question-id')
questionTitle = getQuestionTitleFromDatabase(questionId)
urlSlug = questionTitle.lowercase().replace(" ", "-")
canonical = "https://example.com/questions/" + questionId + "/" + urlSlug

Hard coding https and the domain name in the canonical ensure that the canonical doesn't include alternate versions that are unlike your preferred URLs. Looking up the URL slug from the database ensures that the canonical URL has the correct slug even if the question title changes or if somebody links to a misspelling.