Databases Reference
In-Depth Information
disconnecting when she's finished. Using MySQL from a PHP script is conceptually
similar to using it through the MySQL monitor. The key difference is that you don't
type queries into an interface but instead use PHP library functions to carry out actions
such as connecting to the database server, choosing a database, running a query, and
retrieving the results. We show you an example later in this chapter.
The Apache Web Server
The LAMP platform includes the Apache web server. While it isn't necessary to use
Apache—PHP and MySQL can be used with other web servers—it's our server of
choice in this topic. There are several reasons for this: it's free in a monetary and open
source sense, it's the most popular server on the Web, it's robust and scalable, it is the
web server most commonly used with PHP, and it works on all popular platforms,
including Linux, Windows, and Mac OS X. This section briefly explains web servers
and Apache. We discussed how to configure Apache in Chapter 2.
Web servers are also known as HTTP servers. This describes their function: a web
browser or other web client makes a request for a web resource to a web server using
the HTTP protocol; the web server then serves this request and sends an HTTP response
to the browser. There are essentially two classes of request that web servers can handle:
first, requests for static resources, such as HTML, XML, or PDF documents, and, sec-
ond, requests to run a script—often with parameters provided by the browser request
—and return the output in a response. The latter class is central to web database
applications.
Web browsers send textual requests to web servers. An HTTP request is a text de-
scription of a required resource. For example, the following is what the Lynx browser
sends as a request for the resource
http://www.invyhome.com/artist.php
on the web
server:
GET /artist.php HTTP/1.0
Host: www.invyhome.com
Accept: text/html, text/plain, audio/mod, image/*, video/*, video/mpeg,
application/pgp, application/pgp, application/pdf, message/partial,
message/external-body, application/postscript, x-be2,
application/andrew-inset, text/richtext, text/enriched
Accept: x-sun-attachment, audio-file, postscript-file, default, mail-file,
sun-deskset-message, application/x-metamail-patch, application/msword,
text/sgml, */*;q=0.01
Accept-Encoding: gzip, compress
Accept-Language: en
User-Agent: Lynx/2.8.4dev.16 libwww-FM/2.14 SSL-MM/1.4.1 OpenSSL/0.9.6
The request lists all information required to serve the request: a
method
to use (
GET
),
the required resource, the HTTP version, the host server, and details of the browser
and what types of responses it can receive.
