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

458 Chapter 20 Using Network and Protocol Functions
Listing 20.3
Continued
echo ‘Thank you for submitting your site.’
.’It will be visited by one of our staff members soon.’
// In real case, add to db of waiting sites...
?>
Let’s go through the interesting parts of this script.
First, you take the URL and apply the parse_url() function to it.This function
returns an associative array of the different parts of an URL.The available pieces of
information are the scheme, user, pass, host, port, path, query, and fragment.Typically, you
don’t need all these pieces, but here’s an example of how they make up an URL.
Consider the following URL at http://nobody:secret@example.com:80/
script.php?variable=value#anchor.
The values of each of the parts of the array are
n scheme: http
n user: nobody
n pass: secret
n host: example.com
n port: 80
n path: /script.php
n query: variable=value
n fragment: anchor
In the directory_submit.php script, you want only the host information, so you pull it
out of the array as follows:
$url = parse_url($url);
$host = $url[‘host’];
After you’ve done this, you can get the IP address of that host, if it is in the domain
name service (DNS).You can do this by using the gethostbyname() function, which
returns the IP if there is one or false if not:
$ip = gethostbyname($host);
You can also go the other way by using the gethostbyaddr() function, which takes an
IP as a parameter and returns the hostname. If you call these functions in succession, you
might well end up with a different hostname from the one you began with.This can
mean that a site is using a virtual hosting service where one physical machine and IP
address host more than one domain name.