The three areas where PHP is used

1. Server-side scripting: PHP is most commonly used as a server-side scripting language. To make PHP work as a server-side scripting language, all you need is a PHP parser, a Web server, and a Web browser. However, the Web server has to have a connected PHP installation.
2. Building client-side GUI applications: Although this is not a preferred use of PHP, with a very good working knowledge of PHP you can build your own client-side GUI applications. You can use PHP-GTK, an extension of PHP, which provides an object-oriented interface for building client-side GUI applications.
3. Command-line scripting: Your PHP script can run without any browser or server. In this way, it can be used as a simple and easy-to-use scripting language for tasks such as managing databases and messaging files.

basic of php

PHP is a widely-used general-purpose scripting language that is especially suited for Web development and can be embedded into HTML.

On these blog you find basic help for developing a complete HTML web site through using of PHP scripting language.

First for download php from these web site.
http://windows.php.net/download/

For run php application on your desktop you need a server to install and also install PHP.

As my opinion the WAMP server is best and when you install it the PHP and all nessesary future install it. So you can download wamp server from http://www.wampserver.com/en/ these web site. And editor is NetBeans it’s free to download from http://netbeans.org/downloads/ these site.

PHP stands for Hypertext Pre-Processor. As is suggested by the name, PHP is a pre-processor for hypertext. PHP runs on a remote Web server to process a Web page before it is loaded in a browser. Despite its powerful features, PHP is quite a simple language that has been designed specifically for developing and working with Web pages. Its syntax is similar to that of C and Perl. However, knowledge of both of these languages is not a prerequisite for getting started with PHP, so you can rest easy.

Fundamental feature of PHP

1. ·         It is an open source, server-side scripting language.
2. ·         It is operating-system independent and thus can be used on any operating system, including Microsoft Windows, Mac OS, Linux, HP-UX, and Solaris, to name a few.
3. ·         It supports a wide range of Web servers, such as Apache, Microsoft Internet Information Server, Netscape, and iPlanet.
4. ·         It supports a large number of databases, such as MySQL, Ingres, Sybase, Oracle, Base, Informix, FrontBase, and Unix dbm. One of the distinctive features of PHP is that it provides support to database-driven e-commerce Web sites.
5. ·         It is simpler to write codes in PHP than in other scripting languages.
6. ·         It can be used for creating images, reading/writing files, and sending e-mail. To provide these services, PHP communicates with many protocols, such as HTTP, POP3, SNMP, LDAP, and IMAP.
7. ·         In terms of its performance, you can compare PHP with Active Server Pages (ASP). PHP is popular on Linux platforms, as ASP is popular on Windows. However, cross-platform support provided by PHP makes it score over ASP. PHP can be used as effectively on Windows platforms as on any other platform.
8. ·         Unlike many other scripting languages, such as ASP, PHP comes with a built-in compiler that compiles PHP code and can detect errors in it. You can rectify the mistakes in your PHP code based on the mistakes pointed out by the compiler. No such compiler that compiles ASP code is available with ASP.
9. ·         Another significant feature of PHP is its portability. PHP is compatible with any combination of software, and this is what makes it portable. It can work with almost any combination of operating system, Web server, and database server.

New feature

1. ·         Support for Boolean data type. Support for Java and XML. Support for COM/DCOM. This support is available only for Windows. Support for FTP.
2. ·         The '= = =' operator. In addition to checking whether or not the two values are equal, this operator also checks whether the datatypes of these values are the same or not.
3. ·         The ability to call a function even before it is declared. This is accomplished by using the runtime binding of functions in PHP 4.
4. ·         The PHP highlighter. This feature enables you to view the source code instead of the complete script. This feature helps you to have a faster and better look at the source code.
5. ·         Support for variable assignment by reference. This helps you to link two variables so that the value of one variable is dependent on the value of the other variable. Thus, the value of the variable is updated automatically whenever a value is assigned to another variable.
6. ·         Server API (SAPI). This feature further enhances the support for Web servers.
7. ·         Support for many algorithms, namely Triple DES, MD5, Blowfish, and SHA1. Through the mcrypt library, PHP 4 supports full encryption.
8. ·         The ability to reference variables in PHP 4 by using quotes. Additionally, variable expansion is supported using double quotes.
9. ·         The php.ini file is simple to understand and configure.
10. ·         Better ways of creating classes and objects have been introduced.

The basic concept of class in php and make object of class

Basic class definitions begin with the keyword class, followed by a class name, followed by a pair of curly braces which enclose the definitions of the properties and methods belonging to the class.

The class name can be any valid label which is a not a PHP 

reserved word.  

A valid class name starts with a letter or underscore, followed by any number of letters, numbers, or underscores. As a regular expression, it would be expressed thus: [a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*.

A class may contain its own constants, variables (called "properties"), and functions (called "methods"). 

the simple example of php class is following.

<?phpclass _DemoCLass{
    // property declaration
    public $Member1 = 'Value of Member1';

    // method declaration
    public function DisplayValue() 

    {
        echo $this->var;
    }
}?>

Note:-

The variable name and class name are case sensitive so when you make object of class that time use in proper way else it's give an error.

The pseudo-variable $this is available when a method is called from within an object context. $this is a reference to the calling object (usually the object to which the method belongs, but possibly another object, if the method is called statically from the context of a secondary object).

Make object of class.

//it's create a new object of _DemoCLass class

$NewObj = new _DemoCLass;

 //call method or function of class

$NewObj -> DisplayValue();

for more info visit following link,
http://php.net/manual/en/language.oop5.basic.php