On PHPMaster.com today James Appleyard has put tother a tutorial for the beginners out there about working with strings in PHP, using the huge list of built-in functions to work with your values.
PHP has a vast selection of built-in string handling functions that allow you to easily manipulate strings in almost any possible way. [...] There is no way I can cover every string function in one article, and besides, that is what the PHP manual is for! But what I will do is show how to work with some of the most commonly used string handling functions that you should know. After this, you'll be working with strings as well as any concert violinist!
He shows how to use functions to: change the case of string, remove extra whitespace, get the length, slicing them up and doing replacing on some certain characters. You can find more information on these and the complete list of string functions in PHP in the manual.