Seriously, though; he probably is referring to functions or methods...obviously coming to this site from another background, though.
AFAIK, taglibs in JSP allow you to write an application in Java, put it in a servlet container, and call it from different pages. Given some substantial differences in PHP and Java technologies, I'm not sure I can make a direct analogous reference between taglibs and PHP. For example, code from any PHP source can be [man]include/mand. Data streams and sockets can be accessed or created. PHP can draw images; it can manage network protocols, and interact with other programs without custom library routines being created.
So, what is it he wants to do? I can't tell...