PHP is a server-side
scripting language.
What You Should Already Know
Before you continue you
should have a basic understanding of the following:
- HTML
- Some scripting
knowledge
If you want to study
these subjects first, find the tutorials on our Home page.
What is PHP?
- PHP stands for PHP:
Hypertext Preprocessor
- PHP is a
server-side scripting language, like ASP
- PHP scripts are
executed on the server
- PHP supports
many databases (MySQL, Informix, Oracle, Sybase, Solid, PostgreSQL,
Generic ODBC, etc.)
- PHP is an open
source software
- PHP is free to
download and use
What is a PHP File?
- PHP files can
contain text, HTML tags and scripts
- PHP files are
returned to the browser as plain HTML
- PHP files have
a file extension of ".php", ".php3", or
".phtml"
What is MySQL?
- MySQL is a
database server
- MySQL is ideal
for both small and large applications
- MySQL supports
standard SQL
- MySQL compiles
on a number of platforms
- MySQL is free to
download and use
PHP + MySQL
- PHP combined
with MySQL are cross-platform (you can develop in Windows and serve on a
Unix platform)
Why PHP?
- PHP runs on
different platforms (Windows, Linux, Unix, etc.)
- PHP is
compatible with almost all servers used today (Apache, IIS, etc.)
- PHP is FREE to
download from the official PHP resource: www.php.net
- PHP is easy to
learn and runs efficiently on the server side
Where to Start?
To get access to a web
server with PHP support, you can:
- Install Apache
(or IIS) on your own server, install PHP, and MySQL
- Or find a web
hosting plan with PHP and MySQL support
Basic PHP Syntax
A PHP scripting block
always starts with <?php and ends with ?>. A PHP scripting
block can be placed anywhere in the document.
On servers with
shorthand support enabled you can start a scripting block with <? and end
with ?>.
For maximum
compatibility, we recommend that you use the standard form (<?php) rather
than the shorthand form.
<?php
?>
|
A PHP file normally
contains HTML tags, just like an HTML file, and some PHP scripting code.
Below, we have an
example of a simple PHP script which sends the text "Hello World" to
the browser:
<html>
<body>
<?php
echo "Hello World";
?>
</body>
</html>
|
Each code line in PHP
must end with a semicolon. The semicolon is a separator and is used to
distinguish one set of instructions from another.
There are two basic
statements to output text with PHP: echo and print. In the
example above we have used the echo statement to output the text "Hello
World".
Note: The file must have the .php
extension. If the file has a .html extension, the PHP code will not be
executed.
Comments in PHP
In PHP, we use // to
make a single-line comment or /* and */ to make a large comment block.
<html>
<body>
<?php
//This is a comment
/*
This is
a comment
block
*/
?>
</body>
</html>
|
PHP Variables
Variables are used for
storing values, such as numbers, strings or function results, so that they can
be used many times in a script.
Variables in PHP
Variables are used for
storing a values, like text strings, numbers or arrays.
When a variable is set
it can be used over and over again in your script
All variables in PHP
start with a $ sign symbol.
The correct way of
setting a variable in PHP:
$var_name = value;
|
New PHP programmers
often forget the $ sign at the beginning of the variable. In that case it will
not work.
Let's try creating a
variable with a string, and a variable with a number:
<?php
$txt = "Hello World!";
$number = 16;
?>
|
PHP is a Loosely Typed Language
In PHP a variable does
not need to be declared before being set.
In the example above,
you see that you do not have to tell PHP which data type the variable is.
PHP automatically
converts the variable to the correct data type, depending on how they are set.
In a strongly typed
programming language, you have to declare (define) the type and name of the
variable before using it.
In PHP the variable is
declared automatically when you use it.
Variable Naming Rules
- A variable name
must start with a letter or an underscore "_"
- A variable name
can only contain alpha-numeric characters and underscores (a-z, A-Z, 0-9,
and _ )
- A variable name
should not contain spaces. If a variable name is more than one word, it
should be separated with underscore ($my_string), or with capitalization
($myString)
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