PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

Accessing Form Variables
25
Let’s look at an example that creates easier-to-use copies of variables.
To copy the value of one variable into another, you use the assignment operator,
which in PHP is an equal sign (=).The following statement creates a new variable named
$tireqty and copies the contents of $ POST [‘tireqty’] into the new variable:
$tireqty = $_POST[‘tireqty’];
Place the following block of code at the start of the processing script. All other scripts in
this book that handle data from a form contain a similar block at the start. Because this
code will not produce any output, placing it above or below the and other
HTML tags that start your page makes no difference.We generally place such blocks at
the start of the script to make them easy to find.
This code creates three new variables—$tireqty, $oilqty, and $sparkqty—and sets
them to contain the data sent via the POST method from the form.
To make the script start doing something visible, add the following lines to the bottom
of your PHP script:
echo ‘Your order is as follows: ’;
echo $tireqty.’ tires’;
echo $oilqty.’ bottles of oil’;
echo $sparkqty.’ spark plugs’;
At this stage, you have not checked the variable contents to make sure sensible data has
been entered in each form field.Try entering deliberately wrong data and observe what
happens. After you have read the rest of the chapter, you might want to try adding some
data validation to this script.
Taking data directly from the user and outputting it to the browser like this is a risky
practice from a security perspective. You should filter input data. We will start to cover
input filtering in Chapter 4,“String Manipulation and Regular Expressions,” and discuss
security in depth in Chapter 16,“Web Application Security.”
If you now load this file in your browser, the script output should resemble what is
shown in Figure 1.4.The actual values shown, of course, depend on what you typed into
the form.