php/shell question...

I know that it's pretty easy for a shell script to call a php page to do something. What's the best way to have a php page call a shell script? I'm trying to automate the creation of directories with certain files in them (people creating their own temporary websites..), and figured a simple shell script to copy the files (or symobolic links to these files) from a master directory to the appropriate directory for the customer would make the most sense. Am I barking up the wrong tree, or does this make sense? Thanks in advance, Kelly