PHP is a server site Scripting language
The main features of php is; it is open source scripting language
PHP: Hypertext Preprocessor
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.

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Simple
It is very simple and easy to use, compare to other scripting language it is very simple and easy, this is widely used all over the world.
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Interpreted
It is an interpreted language, i.e. there is no need for compilation.
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Case Sensitive
PHP is case sensitive scripting language at time of variable declaration. In PHP, all keywords (e.g. if, else, while, echo, etc.), classes, functions, and user-defined functions are NOT case-sensitive.
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Open Source
Open source means you no need to pay for use php, you can free download and use.
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Platform Independent
PHP code will be run on every platform, Linux, Unix, Mac OS X, Windows.
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Faster
It is faster than other scripting language e.g. asp and jsp.