php variable

PHP Variables

• PHP variables provide a way to temporarily store data used in a script. Passing PHP variables between functions is a cornerstone of PHP programming; fully understanding their rules and usage in PHP is paramount.
• PHP variable is a temporary memory allocation which used to store data.
• In PHP, variable is declared by "$" sign, we do'nt require to declare data type
  

  In c programming Language	In php
  int a = 34; float a = 45.67; char a = 'aligarh';	$a = 34; $a = 45.67; $a = 'aligarh';





Variable Types

PHP supports eight types of variables

• Half of these are scalar types, meaning they hold only a single value. These are: Booleans (True/False), integers, floating-point numbers, and strings (any quoted character or sequence of characters).
• PHP supports two non-scalar types: 
  1- arrays 
  2-objects. 
• Finally, PHP supports two special types: 
  1 - resources - Resource types provide a pointer-like reference to database connections, opened files and directories, dynamically-generated images, etc. 
  2 - NULL -The NULL type is represented by : the constant NULL

  Naming Conventions

  Variables in PHP must abide by certain naming conventions. Specifically, they
• Variable name start with the dollar sign
• Variable name must contain only letters, numbers, and the underscore
• Variable cannot start with a number
• Variable name are case sensitive
• We can user space in between character of varaible name

Finally, PHP supports two special types: resources and NULL-

• Resourses
• NULL




Resourse

• Resource types provide a pointer-like reference to database connections, opened files and directories, dynamically-generated images, etc.

Null

• The NULL type is represented by:
  the constant NULL 
  -a variable not assigned a value
  -a variable that has been unset