Editing Help:Using Category Trees (section)

=== The <nowiki>{{#categorytree}}</nowiki> parser function ===
You can also use ''parser function'' syntax to place a category tree on a page. This works just like the &lt;categorytree&gt; tag, using a different syntax, e.g. <tt><nowiki>{{#categorytree:Foo}}</nowiki></tt>; options can be specified using the syntax for named template parameters, e.g. <tt><nowiki>{{#categorytree:Foo|hideroot|mode=pages}}</nowiki></tt>.

Using the parser function syntax has the advantage that it allows you to use magic words, templates and template parameters when specifying the category to show. Some examples:
* Using a magic variable to show "this pages" category tree (may be useful on category description pages): <tt><nowiki>{{#categorytree:{{PAGENAME}}}}</nowiki></tt>.
* Using a template to specify the category: <tt><nowiki>{{#categorytree:{{root category}}}}</nowiki></tt> - the name of the root category would be defined by the contents of Template:Root_category.
* Using a template parameter to specify the category, when using CategoryTree inside a template: <tt><nowiki>{{#categorytree:{{{1}}}}}</nowiki></tt> in Template:Baz can be called using <nowiki>{{Baz|Foo}}</nowiki>