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

66 Chapter 2 Storing and Retrieving Data
On most systems, the script runs as the web server user. If your script is on a Unix
system in the ~/public_html/chapter2/ directory, for example, you could create a
world-writeable directory in which to store the order by typing the following:
mkdir ~/orders
chmod 777 ~/orders
Bear in mind that directories and files that anybody can write to are dangerous. In particular,
directories that are accessible directly from the Web should not be writeable. For
this reason, our orders directory is two subdirectories back, above the public_html
directory.We discuss security more in Chapter 15,“E-commerce Security Issues.”
Incorrect permission setting is probably the most common thing that can go wrong
when opening a file, but it’s not the only thing. If you can’t open the file, you really need
to know this so that you don’t try to read data from or write data to it.
If the call to fopen() fails, the function will return false.You can deal with the
error in a more user-friendly way by suppressing PHP’s error message and giving your
own:
@ $fp = fopen(“$DOCUMENT_ROOT/../orders/orders.txt”, ‘ab’);
if (!$fp){
echo " Your order could not be processed at this time. "
.Please try again later.";
exit;
}
The @ symbol in front of the call to fopen() tells PHP to suppress any errors resulting
from the function call. Usually, it’s a good idea to know when things go wrong, but in
this case we’re going to deal with that problem elsewhere.
You can also write this line as follows:
$fp = @fopen(“$DOCUMENT_ROOT/../orders/orders.txt”, ‘a’);
Using this method tends to make it less obvious that you are using the error suppression
operator, so it may make your code harder to debug.
The method described here is a simplistic way of dealing with errors.We look at a
more elegant method for error handling in Chapter 7,“Error and Exception Handling.”
But one thing at a time.
The if statement tests the variable $fp to see whether a valid file pointer was
returned from the fopen call; if not, it prints an error message and ends script execution.
Because the page finishes here, notice that we have closed the HTML tags to give reasonably
valid HTML.
The output when using this approach is shown in Figure 2.3.