When simple variables are just not good enough, arrays come into play (or objects, but that's another topic). The array section in the PHP manual, available at
http://php.net/array, lists approximately 80 functions that are helpful.
Therefore, this tutorial could be filled with array-related code alone. However, not all of these functions are really used often. Therefore, this tutorial presents the most important problems you'll have to solve when working with arrays and, of course, solutions for these problems.