I am just starting out with PHP.  I have resorted to doing some custom PHP programming because the plug-INs for a CMS I am using need a little customization.

The question I have is very simple and I am sure PHP programmers can answer this instantly.  I have successfully declared a global PHP variable.  All I need to know how to do for now is how to declare a button or a hyperlink or an input form element such that it can change the assignment of this variable.