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PHP is a server-side scripting language used for
developing dynamic web pages. PHP actually stands for "PHP: Hypertext
Preprocessor". As you can see, PHP is a recursive acronym. It was
originally developed by Rasmus Lerdorf as a personal tool to keep track
of people who are looking at his online resume. The first version to be
publicly released during 1995 was known as Personal Home Page Tools. It
consisted of a simplistic parser engine which recognized only a few special
macros and special utilities that were used in common home pages back
then. Since then, PHP has evolved into a complex yet easy to learn server-side
scripting language. It is not merely a hypertext preprocessor anymore
due to its ability to generate images and flash application on the fly.
PHP was intended to be implemented in a *Nix Machine (Linux, Unix, FreeBSD,
etc.) and served via an Apache web server but Windows Binary versions
are also available due to the number of Windows users that requested for
the release.
Now the question lies ahead. How does one use PHP?
PHP is a web-based language. It is embedded in HTML code just like ASP.
However, unlike JavaScript, which is also embedded in HTML code, PHP is
a server-side programing language while JavaScript is a client-side scripting
language. Basically, the difference between these two languages is the
fact that the bulk of processing the scripts lies mainly on the server
if it is a server-side script. Client-side scripting puts the bulk on
the client machines. We will not go into detail about these two types.
What we want to get at is the core PHP skills.
PHP is embedded in HTML by using the opening tag
"<?" or "<?php" and closing tag "?>"
without the double quotes. You can insert this anywhere in an HTML document.
For example, consider the undying Hello World PHP script below:
<html>
<head><title>My Hello World Script</title></head>
<body>
<? echo "Hello World!"; ?>
</body>
</html>
This would display "Hello World" with
the default font settings on your browser. Take note that ALL statements
in PHP must end in a semicolon ( ; ). The echo
statement displays one or more strings to the browser. Now let's move
on to something which would be of more use to us.
<html>
<head><title>My Date Script</title></head>
<body>
Hello World! Today is
<?
echo date("l, F j, Y");
?>
</body>
</html>
The script above looks familiar isn't it? It's
the same one used throughout this site to display the current day and
date. The date
function returns formatted date according to the given format. The echo
statement shows the formatted date to the browser. To know more about
the date function and date formats, please visit the official PHP
website.
No programming language is complete without its
control structures. PHP uses the C style of implementing control strictures.
See the example below:
<html>
<head><title>My Date Script</title></head>
<body>
Hello World! Today is
<?
// Display date
echo date("l, F j, Y");
?>
<br>
<?
for ($x=1; $x<=7; $x++)
{
if ($x<4)
{
print "<font size=\"$x\">These words of size $x are small.</font>";
} //end of if
elseif ($x == 4)
{
print "<font size=\"$x\">These words of size $x are medium-sized.</font>";
} // end of elseif
else
{
print "<font size=\"$x\">These words of size $x are huge!.</font>";
} // end of else
} // end of loop
?>
</body>
</html>
Don't let the script above scare you. If you would
look at it line per line, you would notice that is is actually quite easy
to understand. //
are used for one-liner comments. You should use
/* and */
as your starting mark and ending mark respectively for your multi-line
comments.
A typical for
statement like the one above needs an initial value for a counter
variable, a condition that would determine when the loop would
stop, and a counter modifier which either increments or decrements
till it meets or exceeds the condition. All variables start with the $
sign. This lessens the chance of using a reserved word for a variable.
The print
statement is the same as the echo
statement although it is more commonly used.
I guess that's it for a PHP introduction. If you
want a more detailed documentation regarding PHP, visit the official PHP
website.
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