As an update, I believe I have solved my problem and the caching is working for me now.

A note to folks who are doing this on a shared hosting account and following the original poster's instructions:

1) Make sure you use fully qualified path names wherever you need to provide a path, including in the PHP source code sample above.

2) Make sure that you have write permissions on the directory you're asking the Cache_Lite to cache into. In the sample code above the poster used /tmp/ which I didn't notice until tonight; as a shared hosting user I do not have write access to that folder on the server. Just change that path into a fully qualified one to some folder you create in your user folder. Something like ~/pear_tmp/ *without* the tilde.