Base README file updated

Author: me-shaon

README.md

@@ -141,6 +141,44 @@
 
 ## Introduction
 
+PHP is a **dynamic language** with **Weak Typing**. That means you don't have to declare the type of a variable ahead of time. The type will get determined automatically while the program is being processed. That also means that variables are not "bound" to a specific data type.:
+```php
+$foo = "x";    // foo contains a string
+$foo = $foo + 2; // foo concatenates with a number
+echo $foo;  
+```
+
+### Data Types in PHP
+
+PHP supports the following data types:
+
+- Four scalar types:
+
+    - [boolean](http://php.net/manual/en/language.types.boolean.php) (`True` and `False`)
+    - [integer](http://php.net/manual/en/language.types.integer.php) (Positive and negative numbers)
+    - [float](http://php.net/manual/en/language.types.float.php) (Floating point numbers)
+    - [string](http://php.net/manual/en/language.types.string.php) (series of characters)
+
+- Four compound types:
+    - [array](http://php.net/manual/en/language.types.array.php)
+    - [object](http://php.net/manual/en/language.types.object.php)
+    - [callable](http://php.net/manual/en/language.types.callable.php)
+    - iterable
+
+- Two special types
+    - [NULL](http://php.net/manual/en/language.types.null.php)
+    - [resource](http://php.net/manual/en/language.types.resource.php)
+
+
+#### More details about data types in PHP:
+
+- [Data Types - PHP manual](http://php.net/manual/en/language.types.intro.php)
+- [PHP Data Types - W3Schools](https://www.w3schools.com/php/php_datatypes.asp)
+
+#### Object Oriented Programming in PHP
+
+- [Object oriented PHP - Tutorialspoint](https://www.tutorialspoint.com/php/php_object_oriented.htm)
+- [Object oriented PHP for beginners - Tutsplus](https://code.tutsplus.com/tutorials/object-oriented-php-for-beginners--net-12762)
 
 
 ### Big-O Notation and Time Complexity Analysis
@@ -151,6 +189,14 @@
 
 ### How to Use
 
+If you have PHP installed in your machine you can easily run a PHP file using:
+```
+php file_name.php
+```
+If `php` command not working in your terminal/command line, then you might need to add it to your environment Path.
+
 
 ### Useful Links:
 * [Algorithms, 4th Edition (book by: Robert Sedgewick and Kevin Wayne)](http://algs4.cs.princeton.edu/home/)
+* [PHP the right way](http://www.phptherightway.com/)
+* [Hacking with PHP](http://www.hackingwithphp.com/)