In making a program, it should not be forgotten is variable. Variable plays an important role in the process of temporary data storage. Writing variables should also be noted. In writing PHP variables are always denoted by sign ($) in front of variable names. Variable names must consist of one syllable, could also be a combination of numbers with letters, but should not be preceded by the numbers.
Example:
$ NumBook = 23;

Note:
PHP is case sensitive, which means writing small and large very influential. To facilitate the writing of program code, it's worth all the code is written in small letters.

To print the value of a variable can be done in the following ways:
$ Number = 23;
echo $ number