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chapters/variables.md

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+
+The variable is the basic building block of any programming language.
+In PHP, all variables start with a dollar sign.
+```php
+<?php
+
+$greeting;
+```
+
+To set data in a variable, you put an equals sign after it and some data.
+```php
+$greeting = 'Hello World!';
+```
+
+Once you create a variable, you can use it again in other commands and functions.
+```php
+echo $greeting;
+```
+
+After the dollar sign, a PHP variable must have an alphabetic character or underscore. Also, variables are case sensitive.
+```php
+$_var = 'I am a variable with an underscore!';
+$Var = 'I am a variable with a capital letter!';
+$var = 'I am a new variable';
+```
+
+Variables can hold many different types of data, but there are four simple ones you can try now.
+An int is a number without a decimal place.
+A float is a number with a decimal place.
+A boolean can be two values: true or false.
+Last, there is a string: a collection of characters.
+```php
+$int = 1;
+$float = 100.10;
+$bool = true;
+$string = 'I am a string';
+```
+
+In other programming languages, you have to write what type of data the variable will contain.
+PHP keeps it simple by allowing you to put any type of data in a variable, including already used variables.
+```php
+$number = 1;
+$number = 'one';
+```