Update README.

Author: weynhamz

README.md

@@ -2,3 +2,19 @@ phpctags
 ========
 
 An enhanced php ctags file generator.
+
+Using [PHP_Parse](https://github.com/nikic/PHP-Parser) as PHP syntax parsing
+backend, written in pure PHP. The generated ctags index file contains scope
+and access information about the class methods and properties.
+
+This tool was originally developed to enhance the PHP surport for
+[tagbar](http://majutsushi.github.com/tagbar/) vim plugin. The enhaced functionity
+has been included into an addon plugin for tagbar as
+[tagbar-phpctags](https://github.com/techlivezheng/tagbar-phpctags).
+
+enjoy!
+
+Requirements
+============
+
+PHP CLI 5.3+