About PHP 
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the current version of PHP is 5, but 4 is widely used

free, multi-platform

standard configuration known as LAMP

		Linux, Apache, MySQL, and either PHP or perl
		
		variations: MAMP for Mac OS-X
		
		also fancier development environments such as Zend
		
PHP is used on about 75% of all websites, including Wikipedia and Facebook

		incorporated into Wordpress, Joomla, Drupal
		
		main competitor is Micrsoft ASP
		
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php is a scripting language for dynamic web pages

it runs on a server, interpreted when page is requested

		but it can be compiled (FaceBook uses HipHop to compile to C++)
		
php files may contain straight html, and the result of interpreting a php file is most often html

files with extension .php are usually treated as .html by various programs (such as editors)

PHP is often used in conjunction with MySQL, works with other relational databases

a certification test available from Zend.com, results in "Zend Certified Engineer"

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php code is plain text and can be written with many applications

editors such as BBEdit and TextWrangler on Mac color code the syntax

Dreamweaver provides a development environment and tools

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the PHP interpreter executes code between delimiters

		<?php
		?>
		
all other code is passed through as text

comments within php code islands delimited by

		/*
		*/
		
		or lines that begin with #
		
		or the rest of the line after //
		
line breaks and whitespace are usually ignored, php statements end with ;

variables begin with $

C++-like  syntax for if, for...while loops, and most other programming

certain characters within php statements must be escaped with \

quotes are the most frequently escaped characters, and generate the most frequent errors

hundreds of base functions, many libraries

functions can also be defined

PHP supports objects