WP-Wikify

This plugin takes CamelCase words and puts them into links to URLs that incorporate that CamelCase word. If you’ve ever used a wiki, you know what that means.

In version 3.0 support for auto-linking specific words as well as linking using the [[pagename]] and [[pagename|linktext]] notation is supported. Also, in version 3.0, if you have a directory with the files that you want to link to, this can be set up in some configuration parameters. It need not correspond to the path of the link – this can be set in a different configuration parameter.

The code can be found at https://www.andrewsw.com/text/wikifier.txt. Rename it so it ends in .php and put it in your wp-content/plugins directory. Activate it from within the plugins administration interface that is part of WordPress and you should be good to go to use those functions in your templates.

Some example usages and some usage notes follow:

This would not be linked.
ThisWould be linked.
If $useDirectory is set to 1, files are only linked if files with their names (and $pageSuffix appended) can be found in the directory $directoryWithPages (no trailing slash needed). If $useDirectory is set to 0, no test of file existence is done.
$specialWordList = array("co-intentionality", "login");
is a special array used to hold non-CamelCase words to be auto-linked anyway.
$urlPrefix contains the prefix of the url to add - must have a trailing slash.
The defaults correspond to the previous default behavior.
[[this]] would be linked to a page called "this".
[[this|that]] would be the text "that" linked to a page called "this".
With $specialWordList including the word "login", any use of the word "login" will automatically be linked to a page of that name.