In this hour, you learned how to use include() to incorporate files into your documents and to execute any PHP code contained in include files. You learned how to use some of PHP's file test functions. You explored functions for reading files by the line, by the character, and in arbitrary chunks. You learned how to write to files, either replacing or appending to existing content. Finally, you learned how to create, remove, and read directories.
Now that we can work with files, we can save and access substantial amounts of data. If we need to look up data from large files, however, our scripts begin to slow down quite considerably. What we need is some kind of database.