From version 5.0 through 5.1.1, Breadcrumb NavXT included an extra plugin named “Breadcrumb NavXT 5.0 Migration Compatibility Layer”. The purpose of this plugin was to help overcome a bug in WordPress that causes plugin updates to break if the file containing the plugin header changes. Beginning in 5.2.0, Breadcrumb NavXT no longer includes the Breadcrumb NavXT 5.0 Migration Compatibility Layer.

If you still have the Breadcrumb NavXT 5.0 Migration Compatibility layer activated when upgrading to Breadcrumb NavXT 5.2.0 you may see the following PHP warning:

Warning: fopen(…/wp-content/plugins/breadcrumb-navxt/breadcrumb_navxt_admin.php): failed to open stream: No such file or directory in …/httpdocs/wp-includes/functions.php on line 4183
Warning: fread() expects parameter 1 to be resource, boolean given in …/httpdocs/wp-includes/functions.php on line 4186 Warning: fclose() expects parameter 1 to be resource, boolean in …/httpdocs/wp-includes/functions.php on line 4189

As long as Breadcrumb NavXT is activated, the warning message above can be ignored. It is only warning that the Breadcrumb NavXT 5.0 Migration Compatibility Layer was activated but is no longer available. If Breadcrumb NavXT is activated, then the Breadcrumb NavXT 5.0 Migration Compatibility Layer was not doing anything useful.

Migration Compatibility Layer Removal

Updating to Breadcrumb NavXT 5.2 should automatically remove the Breadcrumb NavXT 5.0 Migration Compatibility Layer. However, if you are on an earlier version, you may remove the Breadcrumb NavXT 5.0 Migration Compatibility Layer by performing the following, using a FTP client (or SSH/SCP client) navigate to your WordPress install’s plugins directory. Find the breadcrumb-navxt directory. Within the breadcrumb-navxt directory, there should be a file named breadcrumb_navxt_admin.php, delete this file.

-John Havlik

[end of transmission, stay tuned]

Update 2015-10-04: Beginning with Breadcrumb NavXT 5.3.0, RDFa Breadcrumbs are deprecated in favor of Schema.org BreadcrumbsList, which Google now prefers. Please see the new article on implementing BreadcrumbsList with Breadcrumb NavXT.

While the Google microformats for Breadcrumbs are verbose, ugly, and deprecated, to date, Google still doesn’t support Schema.org breadcrumbs. Thus, we’re going to have to live with the ugly RDFa format for the time being. While there is no ‘one click’ configuration for RDFa breadcrumbs within Breadcrumb NavXT, support for them is not too difficult to configure.

Calling Code Modifications

To begin, the wrapping div for the calling code needs to have xmlns:v="http://rdf.data-vocabulary.org/#" added to it. Below is an example calling code block for users of the regular bcn_display(); function.

<div class="breadcrumbs" xmlns:v="http://rdf.data-vocabulary.org/#">
    <?php if(function_exists('bcn_display')) { bcn_display(); }?>
</div>

Settings Modifications

In general, you need a

<span typeof="v:Breadcrumb">

wrapping around every breadcrumb, and an inner element containing property="v.title" and rel="v:url" if the breadcrumb contains a link. For the most part this will result in two replacements need to be made to all of the breadcrumb templates. For the linked breadcrumb templates, replace:

<a title="Go to %title%." href="%link%">%htitle%</a>

with:

<span typeof="v:Breadcrumb"><a rel="v:url" property="v:title" title="Go to %title%." href="%link%" class="%type%">%htitle%</a></span>

Note the extra span containing the typeof declaration. This is necessary for Google to pick up on the breadcrumb objects (even though the tag is redundant as the property should work on the anchor).

For the unlinked breadcrumb templates, replace:

%htitle%

with:

<span typeof="v:Breadcrumb"><span property="v:title">%htitle%</span></span>

To jumpstart this replacement process, you can import the following Breadcrumb NavXT settings XML file. Breadcrumb NavXT RDFa Breadcrumbs settings file (Right click and select “Save As”).

One Last Thing

Depending on the version of Breadcrumb NavXT, the typeof attribute may not be accepted in the settings (it will get automatically stripped out). To fix this follow the process outlined in How to Add li and Other Tags to Breadcrumb Templates to add the typeof attribute to the span HTML tag. Otherwise, wait for Breadcrumb NavXT 5.1 (or 5.0.2) to be released.

-John Havlik

[end of transmission, stay tuned]