PHP & MySQL: The Missing Manual, 2nd Edition

Chapter 4. MySQL and SQL: Database and Language

Where is this supposed to go?

It’s a question you ask every day. Where do these shoes go? Where does this new box of books go? Where do these receipts go? Because that’s such a common question, it shouldn’t surprise you too much that when you’re building web applications, you need to ask the same thing:

Where does my information go?

For the kinds of web applications you’ve been building with web pages and PHP, the answer to this question is simple: in a database. But what do you get out of a database that makes it worth the effort of installing another tool and learning another language? And, why does everyone seem to agree that if you’re writing PHP code, you need a database, too? Sit tight, because this chapter is about to reveal all.

What Is a Database?

A database is just a repository in which you can store information, add some layer of organization to the stored information, and grab that information when it’s needed. In a literal sense, a file cabinet is a database. You can throw things into it, pull those things back out, and even use files and labels to keep your files organized.

Databases Are Persistent

You’ve already seen that PHP gives you arrays (The $_REQUEST Variable Is an Array) that serve as a sort of programmer’s file cabinet. An array might function as a database in a simplistic sense, but it won’t serve your needs for long. For one thing, arrays and their contents in PHP are lost every time your program stops and starts ...