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

Using Network Lookup Functions
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The best use of this approach is to combine information from different sources to add
some value.You can see one good example of this approach in Philip Greenspun’s infamous
script that produces the Bill Gates Wealth Clock at http://philip.greenspun.com/
WealthClock.
This page takes information from two sources. It obtains the current U.S. population
from the U.S. Census Bureau’s site. It also looks up the current value of a Microsoft share
and combines these two pieces of information, adds a healthy dose of the author’s opinion,
and produces new information—an estimate of Bill Gates’ current worth.
One side note: If you’re using an outside information source such as this for a commercial
purpose, it’s a good idea to check with the source or take legal advice first.You
might need to consider intellectual property issues in some cases.
If you’re building a script like this, you might want to pass through some data. For
example, if you’re connecting to an outside URL, you might like to pass some parameters
that would normally be typed in by the user. If you’re doing this, it’s a good idea to
use the urlencode() function.This function takes a string and converts it to the proper
format for an URL; for example, transforming spaces into plus signs.You can call it like
this:
$encodedparameter = urlencode($parameter);
One problem with this overall approach is that the site you’re getting the information
from may change its data format, which will stop your script from working.
Using Network Lookup Functions
PHP offers a set of “lookup” functions that can be used to check information about
hostnames, IP addresses, and mail exchanges. For example, if you were setting up a directory
site such as Yahoo! when new URLs were submitted, you might like to automatically
check that the host of an URL and the contact information for that site are valid.
This way, you can save some overhead further down the track when a reviewer comes to
look at a site and finds that it doesn’t exist or that the email address isn’t valid.
Listing 20.2 shows the HTML for a submission form for a directory like this.
Listing 20.2 directory_submit.html—HTML for the Submission Form
Submit your site
Submit site
URL:
Email contact: