Our focus for this series of postings has been on the problems associated with getting information from one page to another in a stateless, Internet environment, where nothing is saved from one web page to the next. How do we pass the items you want to purchase from the form submission page to the shopping cart web page, for example.
We now will move on to passing data, variables, around the various files in your web application. This assumes you've obtained information from the user with a post, or get, or a cookie, or a call to the database, and have assigned that snippet of information to a variable name, like this:
//using the form GET method $fname = $_GET['firstname']; // using the form POST method $lname = $_POST['lastname']; // using cookie information $city = $_COOKIE['usercity']; // using a function to call the information from the database $addr = getaddr( $username );
We'll focus on taking variables, in this example: $fname, $lname, $city, or $addr to the next PHP file on the server, you'll use to either display the variable, or use the variable in your application. Since php is a scripting, or interpretive language, when you open up a new file it stands on its own, and any data, or variables you'll need, will have to be explicitly passed to that file. How we do that will be the subject of the next series of posts.
Since most modern languages use object-oriented software, and PHP, is no exception, we will eventually get to passing entire objects to other files and ways to persist objects in your application, but let's not get ahead of ourselves, we'll start with sessions and passing information with a session variable.