I think what Rarst means is that it is a .file (or hidden file) much like the .htaccess file. If you are browsing your files, there is an option to show hidden files. Once that option is chosen, you will most likely also see the .maintenance file
I ended up duplicated /includes/templates-media-wp41.php and renaming it to templates/media-wp42.php
The problem was caused by about 8 wordpress files in the root directory with a filesize of 0 bytes. Uploading fresh copies of these files (from the latest version downloaded from wordpress.org) solved the initial problem. The subsequent problem has since cleared without any indication of what steps solved it.
HTTPS Warning and Certificate Error when Updating Network
wp_get_archives custom function broken since upgrading to WP 3.7.1
based on https://wordpress.org/support/topic/wp-admin-returning-500-errors-after-update-to-421, seems like it was related to the conversions of tables to utf8mb format done in 4.2 which timeout when there are many comment. Possible solutions: make the DB upgrade on some staging server in which all timeouts are off, or increase the timeout on the production server until it works.
Upgrading Across Multiple Versions
I checked in mysql and the type of the column it was looking for is text and in version 5.1 of MySQL that I am using the size is 65,535 so I replaced line 1461 which was giving error with the following hardcoded size: $content_length = array( ‘type’ => ‘byte’, ‘length’ => 65535, ); After … Read more
What that error is saying is that $labels is an empty object, so it can’t assign to it. $foo = NULL; $foo->labels = false; // This causes the error See this Stack Overflow post for technical details: https://stackoverflow.com/questions/8900701/creating-default-object-from-empty-value-in-php
Does your plugin use a version number? On plugin activation you can compare the version number and use the code you have above to remove the ‘old’ options if they exist. if ( $myplugin_version > 3.0 ) { // Remove all plugin options with the prefix “myplugin_” }