Automatically add hreflang tags in WordPress subdirectory multisite

Question

We have a WordPress MU subdirectory network setup:

• www.example.com - Main site, US, Worldwide
• www.example.com/uk/ - Display
to UK visitors
• www.example.com/au/ - Displayed to Australian visitors.

We want to add hreflang tags to every web page and exclude locations custom post types.

From this question, I adapted the code in the child theme functions.php To:

function add_hreflang_attribute() {
   $site_url = network_site_url(); // base URL
   $alt_langs = array( '', 'au', 'uk' ); // two-letter language code
   $page_path = substr(get_permalink(), strlen(home_url('/'))); // path of page after base URL
   
   if (!( is_singular( 'locations' ) ) ) {
           
       // loop through the alternative languages, and get the appropriate hreflang tag for each that exists
       foreach ($alt_langs as $lang) {
           $updated_url_lang_path = $site_url . $lang . '/' . $page_path;
           $url_headers = @get_headers($updated_url_lang_path);
           if($url_headers && strpos( $url_headers[0], '200')) {
               if ($lang == 'uk') {
                   echo '<link rel="alternate" href="' . $updated_url_lang_path . '" hreflang="en-gb" />'. PHP_EOL;
               } elseif ($lang == '') {
                 
               }
               else {
                   echo '<link rel="alternate" href="' . $updated_url_lang_path . '" hreflang="en-' . $lang . '" />'. PHP_EOL;
               }
           }
       }
       
       // set primary as x-default
       echo '<link rel="alternate" href="' . $site_url . $page_path . '" hreflang="x-default" />';
        
   }

}

This code applies to the main website's homepage and example pages: www.example.com/features/;

<link rel="alternate" href="https://www.example.com/au/features/" hreflang="en-au" />
<link rel="alternate" href="https://www.example.com/uk/features/" hreflang="en-gb" />
<link rel="alternate" href="https://www.example.com/features/" hreflang="x-default" />

It applies to:

• Home page of the AU website,
• Features page of the AU website: https://www.example.com/au/features/,

But on www.example.com/uk/ it only produces:

<link rel="alternate" href="https://www.example.com/au/" hreflang="en-au" />
<link rel="alternate" href="https://www.example.com/" hreflang="x-default" />

Lack:

<link rel="alternate" href="https://www.example.com/uk/" hreflang="en-gb" />

The feature page is a simple WordPress page.

Thanks for the help.

edit

If I add if ($lang == 'uk') {print_r(get_headers($updated_url_lang_path));}, I see:

Array
(
    [0] => HTTP/1.1 200 OK
    [1] => Server: nginx
    [2] => Date: Wed, 11 May 2022 22:08:04 GMT
    [3] => Content-Type: text/html; charset=UTF-8
    [4] => Content-Length: 88422
    [5] => Connection: close
    [6] => Vary: Accept-Encoding
    [7] => Vary: Accept-Encoding
    [8] => Accept-CH: Sec-CH-UA-Mobile
    [9] => Link: <https://www.example.com/uk/wp-json/>; rel="https://api.w.org/"
    [10] => Link: <https://www.example.com/uk/wp-json/wp/v2/pages/10>; rel="alternate"; type="application/json"
    [11] => Link: <https://www.example.com/uk/>; rel=shortlink
    [12] => X-Powered-By: WP Engine
    [13] => X-Cacheable: SHORT
    [14] => Vary: Accept-Encoding,Cookie
    [15] => Cache-Control: max-age=600, must-revalidate
    [16] => X-Cache: HIT: 8
    [17] => X-Cache-Group: normal
    [18] => Accept-Ranges: bytes
    [19] => X-Orig-Cache-Control: no-cache
)

and add the following correctly:

<link rel="alternate" href="https://www.example.com/uk/" hreflang="en-gb" />

However, I can only see this when logged into WordPress.

In an incognito window, at https://www.example.com/uk/ I see (only):

<link rel="alternate" href="https://www.example.com/" hreflang="x-default" />

Answer 1

Hey Steve, use this code, it will work great! ! !

function mm_add_hreflang_attribute() {
if (!( is_singular( 'locations' ) ) ) {
    $sites = array(
        array('', 'x-default'),
        array('en-gb/', 'en-gb'),
        array('en-au/', 'en-au'),
    );
    
    if ( is_post_type_archive('locations') ) {
        foreach ( $sites as $site ) {
            $site_url = network_site_url();
            $page_path = 'locations/';
            $geo_url = $site[0];
            $hreflang = $site[1];
            $url = $site_url . $geo_url . $page_path;
            echo ''. PHP_EOL;
        }
    } 
else 
{
 foreach ( $sites as $site ) {
    $site_url = network_site_url();
    $page_path = substr(get_permalink(), strlen(home_url('/')));
    $geo_url = $site[0];
    $hreflang = $site[1];
    $url = $site_url . $geo_url . $page_path;
    echo ''. PHP_EOL;
    }
   }
  }
}
add_action('wp_head', 'mm_add_hreflang_attribute', 1);

Answer 2

I changed the code to:

function mm_add_hreflang_attribute() {
    if (!( is_singular( 'locations' ) ) ) {
        $sites = array(
            array('', 'x-default'),
            array('en-gb/', 'en-gb'),
            array('en-au/', 'en-au'),
        );
        
        if ( is_post_type_archive('locations') ) {
            foreach ( $sites as $site ) {
                $site_url = network_site_url();
                $page_path = 'locations/';
                $geo_url = $site[0];
                $hreflang = $site[1];
                $url = $site_url . $geo_url . $page_path;
                echo ''. PHP_EOL;
            }
        } else {
            foreach ( $sites as $site ) {
                $site_url = network_site_url();
                $page_path = substr(get_permalink(), strlen(home_url('/')));
                $geo_url = $site[0];
                $hreflang = $site[1];
                $url = $site_url . $geo_url . $page_path;
                echo ''. PHP_EOL;
            }
        }
    }
}
add_action('wp_head', 'mm_add_hreflang_attribute', 1);

good results.