mu-domain-mapping conflict with Customizer

I just solved this on my own site, with 2 fixes:

1. In your themes function.php, add:

remove_action( 'admin_init', 'dm_redirect_admin' );
add_action( 'admin_init', 'theme_redirect_admin' );
function theme_redirect_admin() {
	// don't redirect admin ajax calls
	if ( strpos( $_SERVER['REQUEST_URI'], 'wp-admin/admin-ajax.php' ) !== false )
		return;

	// Added 2016-01-25 by CH - && !is_customize_preview()
	if ( get_site_option( 'dm_redirect_admin' ) && !is_customize_preview() ) {
		// redirect mapped domain admin page to original url
		$url = get_original_url( 'siteurl' );
		if ( false === strpos( $url, $_SERVER[ 'HTTP_HOST' ] ) ) {
			wp_redirect( untrailingslashit( $url ) . $_SERVER[ 'REQUEST_URI' ] );
			exit;
		}
	} else {
		global $current_blog;
		// redirect original url to primary domain wp-admin/ - remote login is disabled!
		$url = domain_mapping_siteurl( false );
		$request_uri = str_replace( $current_blog->path, '/', $_SERVER[ 'REQUEST_URI' ] );
		if ( false === strpos( $url, $_SERVER[ 'HTTP_HOST' ] ) ) {
			wp_redirect( str_replace( '//wp-admin', '/wp-admin', trailingslashit( $url ) . $request_uri ) );
			exit;
		}
	}
}

2. Check this box in the ‘Domain Mapping’ settings:
Redirect administration pages to site's original domain (remote login disabled if this redirect is disabled)

A related note, if you need the Admin Bar links to work, they have to be changed like this for each link Node.

add_action( 'admin_bar_menu', 'customize_admin_links', 999 );
}
function customize_admin_links( $wp_admin_bar ) {
	$args = array(

		'id'     => 'customize',
		'href'  => 'https://example.com/wp-admin/customize.php',
	);
	$wp_admin_bar->add_node( $args );
}

Edited for consistent names

thank you VERY MUCH chenryahts –

silly question, but what happens during the next release? does all this code get clobbered?

i was considering removing customizer.

As long as you put that in your theme functions.php file, it will last through an update (it may be unnecessary or wrong, but it won’t disappear).

As far as the Customizer, I’d recommend leaving it in, as WP is encouraging designers to use it more by requiring theme customizations use it.

Hope this helps.

once again, chenryahts, thank you very much.

i am wondering if the plugin author is seeing this, and might respond.

@edwardsmarkf If I understood correctly you want to keep the plugin set to “Redirect administration pages to site’s original domain” AND make possible to users use customizer.

I solved this by modifying 2 lines in the plugin file and checking if there’s an customizer object. If there is, the redirection doesn’t happen.

function dm_redirect_admin() {// line 607 on WordPress MU Domain Mapping 0.5.5.1
	// don't redirect admin ajax calls
	if ( strpos( $_SERVER['REQUEST_URI'], 'wp-admin/admin-ajax.php' ) !== false )
		return;
	global $wp_customize; // gets $wp_customize global
	if ( get_site_option( 'dm_redirect_admin' ) && !isset($wp_customize) ) { // redirects to original url only if $wp_customize is not set
		// redirect mapped domain admin page to original url
		$url = get_original_url( 'siteurl' );
		if ( false === strpos( $url, $_SERVER[ 'HTTP_HOST' ] ) ) {
			wp_redirect( untrailingslashit( $url ) . $_SERVER[ 'REQUEST_URI' ] );
			exit;
		}
	} else {
		global $current_blog;
		// redirect original url to primary domain wp-admin/ - remote login is disabled!
		$url = domain_mapping_siteurl( false );
		$request_uri = str_replace( $current_blog->path, '/', $_SERVER[ 'REQUEST_URI' ] );
		if ( false === strpos( $url, $_SERVER[ 'HTTP_HOST' ] ) ) {
			wp_redirect( str_replace( '//wp-admin', '/wp-admin', trailingslashit( $url ) . $request_uri ) );
			exit;
		}
	}
}

Remember to backup the original plugin files (or use a versioning system to keep track of change).

You can see both the original and the modified functions on https://gist.github.com/2aces/530ba377c5a9a590332f6eadaed8092d#file-dm_redirect_admin_customizer-php and the code belows