Apply Canonical tag to basic PHP sites

header.php

<?php 

    /**
     * Apply correct canonical tag for Forest Drive and Resin
     * @author Freelance SEO Essex
     * @link https://www.freelanceseoessex.co.uk/
     */
    $actual_link = (isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] === 'on' ? "https" : "http") . "://$_SERVER[HTTP_HOST]$_SERVER[REQUEST_URI]";
    $dirname       = pathinfo($actual_link)['dirname'];
    if( $dirname === 'http:' ) {
      $dirname = 'http://';
    }
    if( $dirname === 'https:' ) {
      $dirname = 'https://';
    }
    $basename      = pathinfo($actual_link)['basename'];
    $extension     = pathinfo($actual_link)['extension'];
    $canonical_url = $dirname . $basename;
    if( $extension === 'php' ) {
      $basename      = str_replace('.php', '', $basename);
      $canonical_url = $dirname . '/' . $basename;
    }