PHP Constant

PHP Constant

A constant in PHP is a name or an identifier for a simple value. A constant value cannot change during the execution of the PHP script.

• By default, a PHP constant is case-sensitive.
• By convention, constant identifiers are always uppercase.
• A constant name starts with a letter or underscore, followed by any number of letters, numbers, or underscore.
• There is no need to write a dollar sign ($) before a constant, however one has to use a dollar sign before a variable.

PHP Magic Constant

PHP has nine predefined constants that change value depending on where they are used, and therefor they are called "magic constants". These magic constants are written with a double underscore at the start and the end, except for the ClassName::class constant.