About PHP : PHP (recursive acronym for PHP: Hypertext Preprocessor) is a widely-used open source general-Purpose scripting
language that is especially suited for web development and can be embedded into HTML.

10 Famous Websites Developed With PHP 

• Yahoo: One of the most trafficked website on the planet with more than 627 million unique visitors per month.
• FaceBook: It is no secret that Facebook makes use of PHP in the user end.
• Wikipedia: The best free source for all kinds of information over web Wikipedia is developed using a software called MediaWiki which is written in PHP.
 • Flickr: The web's leading photo sharing site hosting over 2.5 billion images uses PHP.
• WordPress.com: Wordpress is also developed using PHP and JavaScript and in addition to that Kluery library is also used for animating, event handling.
• Friendster: One of the largest social networking sites. It was founded in 2003. A Global traffic rank of 16,443 on Alexa and over 50 million users.
• Digg: a user driven social content website uses PHP too. SourceForge.net: The world's largest Development and Download repository of Open Source code and applications.
• iStockPhoto: A royalty-free stock photo provider and most likely the most popular online photo library.lt is now owned by Getty Images.
• LiveBid Auctions: A part of Amazon.com and the leading provider of live-event auctions on the Internet. 

List application made in php

•  Developing Facebook Applications
•  Building an Online Community
•  Project Management Tools
•  E-Commerce
•  Mailing Lists
•  Image Processing and Generation
•  Content Management Systems
•  Create a PHP Photo Gallery 

What is the job outlook for PHP developers?

Although government analysts celebrate faster than average job growth for computer programmers, PHP developers face a few hurdles to long-term job security:
  Narrow niche. Few large employers use PHP for major projects, despite the sudden growth of Web application companies that built their businesses on PHP code. Most PHP developers market themselves as experts on the databases their code manipulates.
 Free code. PHP's growth through the open source movement changes the employment equation for programmers who want to become PHP developers. Stock code modules can be found for free or cheap online, leaving employers fewer reasons to hire developers to write code from scratch.

Freelance tendencies. Many companies require PHP developers only in short bursts, relying on teams of freelancers and outside service providers instead of on in-house talent.

Offshore challenges. Some employers use in-house PHP developers as project managers and architects, tarn out original code to inexpensive teams in places like India, Romania and the Philippines.

PHP developers enjoy a meritocracy hard to match in the IT profession. With most PHP code "in the open" for peers a potential employers to review, solid code acts as both a calling card and a performance evaluation.

What can php do? 

• PHP can generate dynamic page content
• PHP can create, open, read, write, and close files on the server
• PHP can collect form data
• PHP can send and receive cookies
• PHP can add, delete, and modify data in your database
• PHP can restrict users to access some pages on your website
• PHP can encrypt data