Yeah, I think this is a memory issue. First of, this plugin uses output buffering for the shortcode, not for the widget. I think another (memory exhausted) error occurs just after starting the output buffering (which we don’t get to see). There’s a possibility it’s unrelated to this plugin. The memory usage by other plugins/themes that load before this plugin could just be to much, so when it reaches this plugin it fails when inside the output buffer. That’s why I asked you to try with other plugins de-activated. I know this is probably too much info 🙂
Here are three ways to increase PHP’s memory allocation:
1. If you can edit or override the system php.ini file, increase the memory limit. For example, memory_limit = 128M
2. If you cannot edit or override the system php.ini file, add php_value memory_limit 128M at the top of your .htaccess file.
3. If neither of these work, it’s time to ask your hosting provider to temporarily increase PHP’s memory allocation on your account. Keep in mind that most decent hosting providers allocate 32 MB to PHP under each account, and most decent hosting providers allow users to temporarily increase the memory allocation.
http://codex.wordpress.org/Common_WordPress_Errors#Allowed_memory_size_exhausted
If that doesn’t work you can add a filter to the widget in your (child) theme’s functions.php file to limit the search for related posts.
add_filter( 'related_posts_by_taxonomy_widget_args', 'rpbt_limit_by_months', 10, 2 );
function rpbt_limit_by_months( $args, $instance ) {
$args['limit_month'] = 6;
return $args;
}
btw:
consider creating a child theme instead of editing your theme directly – if you upgrade the theme all your modifications will be lost. Or create a plugin with the code above.
Another option is to download the next version that comes out next week (version 2.0.0), it has a small optimization for the query to get the related posts.
https://downloads.wordpress.org/plugin/related-posts-by-taxonomy.zip
