php|architect's Guide to Web Scraping with PHP - Wind Business ...

10 ” HTTP
http://en.wikipedia.org/wiki/Main_Page
requested resource.
is the resulting full URL of the
i
URI vs URL
URI is sometimes used interchangeably with URL, which frequently leads to confusion
about the exact nature of either. A URI is used to uniquely identify a resource, indicate
how to locate a resource, or both. URL is the subset of URI that does both (as opposed
to either) and is what makes them usable by humans. After all, what’s the use of being
able to identify a resource if you can’t access it! See sections 1.1.3 and 1.2.2 of RFC 3986
for more information.
GET is by far the most commonly used operation in the HTTP protocol. According
to the HTTP specification, the intent of GET is to request a representation of a
resource, essentially to “ read” it as you would a file on a file system. Common examples
of formats for such representations include HTML and XML-based formats
such as XHTML, RSS, and Atom.
In principle, GET should not modify any existing data exposed by the application.
F or this reason, it is considered to be what is called a safe operation. It is worth
noting that as you examine your target applications, you may encounter situations
where GET operations are used incorrectly to modify data rather than simply returning
it. This indicates poor application design and should be avoided when developing
your o wn applications.
Anatomy of a URL
If you aren’t already familiar with all the components of a URL, this will likely be
useful in later chapters.
http://user:pass@www.domain.com:8080/path/to/file.ext?query=&var=value#anchor
• http is the protocol used to interact with the resource. Another example is
https, which is equivalent to http on a connection using an SSL certificate for
encryption.
• user:pass@ is an optional component used to instruct the client that Basic
HTTP authentication is required to access the resource and that user and pass