Conditional config WP_HOME/WP_SITEURL does not update bloginfo('template_url')?

Question

The scenario:

This question relates to Wordpress theme development on a local environment via MAMP.

In order to enable mobile device testing via xip.io, I have modified my local Wordpress wp-config.php file with the following:

require_once('b5f-browsers.php');
if( b5f_browser_check('mobile')) {
    define('WP_HOME','http://mysite.dev.'.$_SERVER['SERVER_ADDR'].'.xip.io');
    define('WP_SITEURL','http://mysite.dev.'.$_SERVER['SERVER_ADDR'].'.xip.io');
}

NOTE: Credit for this solution goes to brasofilo in this related post.

---

The problem:

My custom theme's HTML head and footer blocks contain calls to CSS and JavaScript files using the standard bloginfo('template_url') function. This works normally when browsing on the host computer.

But on mobile devices, the main site base domain as defined under WP Admin > Settings > General is used in the 'template_url' instead of the conditional override as specified in the wp-config.php file above.

So I get lines like this:

<link rel="stylesheet" href="http://mysite.dev/wp-content/themes/mytheme/style.css">

Instead of this:

<link rel="stylesheet" href="http://mysite.dev.HOST-IP-ADDRESS.xip.io/wp-content/themes/mytheme/style.css">

---

A workaround:

Interestingly, I noticed that bloginfo('wpurl') returns the correct xip.io URL for mobile, and other core Wordpress functions such as bloginfo('rss_url') obey the URL override. But bloginfo('template_url') just doesn't seem to want to do it.

So as a workaround, I am using bloginfo('wpurl') then adding the full path to the theme directory instead:

<link rel="stylesheet" href="<?php bloginfo('wpurl'); ?>/wp-content/themes/mytheme/style.css">

But this doesn't seem like the right way to go about it...

---

The question:

Is there a better/correct way to handle this?

Answer 1

Found the solution... the problem was due to placement of the conditional statement in the wp-config.php file.

It needed to be inserted before the require_once(ABSPATH . 'wp-settings.php'); line near the bottom of the default config file, otherwise the constants are already defined and cannot be redefined.

So final section of the wp-config.php file now looks like this:

...

/** Add xip.io support for mobile theme testing **/
require_once('b5f-browsers.php');
if( b5f_browser_check('mobile')) {
    define('WP_HOME','http://mysite.dev.'.$_SERVER['SERVER_ADDR'].'.xip.io');
    define('WP_SITEURL','http://mysite.dev.'.$_SERVER['SERVER_ADDR'].'.xip.io');
}

/* That's all, stop editing! Happy blogging. */

/** Absolute path to the WordPress directory. */
if ( !defined('ABSPATH') )
define('ABSPATH', dirname(__FILE__) . '/');

/** Sets up WordPress vars and included files. */
require_once(ABSPATH . 'wp-settings.php');

Answer 2

My quick guess (that code is rather nightmarish to follow) would be that you need to define WP_CONTENT_URL as well, since issue seem to be about content directories.