- Passive content:
- We refer to webpages as passive content (because they do not perform any operations)
- Active content:
- The web server
can also
execute programs
stored in a pre-defined (set up by the installer)
directory.
- When these programs are run,
they will
produce (output) a
HTML file
(i.e., web pages ) !!!
- In other words, active content are web pages that are created dynamically (by the execution of a program)
Experiment: click on the following hyperlink:
Reload the webpage to see changes to the webpage.
Explanation:
- When you click on the:
http://holland.mathcs.emory.edu/~cs377001/intro/random-text.php link,
the browser sends the HTTP request message to holland.mathcs.emory.edu requesting the webpage "random-text.php" from user cs377001:
- Because the
file extension is
.php, the
web server will
run the
PHP script and
obtain the
output of the
PHP program:
- The
output of the
PHP program
/home/cs377001/public_html/intro/random-text.php
is then
returned (in an HTML message)
by the web server:
Note:
- The
output of the
PHP program
is a
web page !!!!
I.e.: the PHP program "creates" a webpage when the PHP program is executed !!!!
- The
output of the
PHP program
is a
web page !!!!
- The web browser receives the
web-server's message
and
then "renders" the
content
in the browser's window:
- The web server
can also
execute programs
stored in a pre-defined (set up by the installer)
directory.
- Demo:
(Demo above interaction)
How to do the demo:
- Open
this webpage in browser:
- Right click on the
webpage and
select
View source page
- Run this
command on
holland.cs.emory.edu:
php /home/cs377001/public_html/intro/random-text.phpCompare the output of the command with the source of the webpage: they are the same !!!
(Run a few times to get the same random text....)
- Open
this webpage in browser:
- Comment:
- A common application of
active content
is an
online ordering system
(like Amazon)
(your shopping basket is different each time you click the check out page )
- A common application of
active content
is an
online ordering system
(like Amazon)
- The current technologies that enable
the web-server
to execute
programs
uses:
- A server-side scripting language
-
Operation of
the server-side scripting
technique:
- The Web server is
augmented
with the capabity to
execute
program (= "scripts") written
in a "scripting" language
- Scripting language = a high level programming language that allow fast prototyping and program development
- The web pages (HTML files)
can contain
beside HTML code:
- Program statements written in a scripting language
- The web server
will:
- Execute the program
- Obtain the output produced by the execution
- Return the output of the program as a webpage !!!
- The Web server is
augmented
with the capabity to
execute
program (= "scripts") written
in a "scripting" language
- Examples
of server-side
scripting languages
- ASP (Active Server Pages click here)
- Perl
- Phyton
- PHP
- (Too many to list)
We will study PHP (PHP Hypertext Preprocessor)
- Why I picked
PHP to
teach web-programming:
- Widely used
(not the
main reason I picked
PHP)
-
Very similar to
Java/C
(I can teach you PHP programming in 1 lecture !!!!!!)
The focus is database access --- but we need to learn a new programming language so that we can use this server-side scripting language to access MySQL
- Web-programming in PHP is much easier than with other scripting languages
- Widely used
(not the
main reason I picked
PHP)
- PHP
(Wikipedia:
click here)
- PHP is an open source
general-purpose
server-side scripting language
originally designed for Web development to produce
dynamic Web pages.
- PHP is installed on more than 20 million Web sites and 1 million Web servers
- PHP is an open source
general-purpose
server-side scripting language
originally designed for Web development to produce
dynamic Web pages.
- Coverage:
- PHP is a
general purpose scripting language
- I.e.: it is a complete programming language
There is no way we can discuss all features of PHP in such a short time !!!
- We will cover sufficient features to allow you to access a (MySQL) database through server-side scripting.
- PHP is a
general purpose scripting language
- There is a
great
online manual on PHP
at this website
(where this material is based on)
if you need
further info:
click here
- Availability:
- PHP is only installed on holland.mathcs.emory.edu
- Working with
PHP scripts:
- First, remote login to
holland.mathcs.emory.edu:
ssh -X holland.mathcs.emory.edu
- You must work inside
your public_html
directory to
keep your work
private:
cd ~/public_html
- PHP scripts in this
directorty can also
by access as a
webpage through the hyperlink:
http://holland.mathcs.emory.edu/~yourID/filename
- First, remote login to
holland.mathcs.emory.edu:
- Note:
- You can make sub-directories to store PHP scripts