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

580 Chapter 27 Building User Authentication and Personalization
This is the first script with any complexity to it that we have looked at in this application.
It begins by including the application’s function files and starting a session. (When
the user is registered, you create his username as a session variable, as you did in
Chapter 23,“Using Session Control in PHP.”)
The body of the script takes place in a try block because you check a number of
conditions. If any of them fail, execution will fall through to the catch block, which we
look at shortly.
Next, you validate the input data from the user. Here, you must test for the following
conditions:
n Check that the form is filled out.You test this with a call to the function
filled_out(), as follows:
n
if (!filled_out($_POST))
We wrote this function ourselves. It is in the function library in the file
data_valid_fns.php.We look at this function shortly.
Check that the email address supplied is valid.You test this as follows:
if (valid_email($email))
n
Again, this is a function we wrote; it’s in the data_valid_fns.php library.
Check that the two passwords the user has suggested are the same, as follows:
if ($passwd != $passwd2)
n
Check that the username and password are the appropriate length, as follows:
if ((strlen($passwd) < 6)
and
if ((strlen($passwd) > 16)
In the example, the password should be at least 6 characters long to make it harder
to guess, and the username should be fewer than 17 characters so that it will fit in
the database. Note that the maximum length of the password is not restricted in
this way because it is stored as an SHA1 hash, which will always be 40 characters
long no matter the length of the password.
The data validation functions used here, filled_out() and valid_email(), are shown
in Listings 27.7 and 27.8, respectively.