PHP Tutorial
PHP Constants
PHP Constants are global variables whose value cannot be changed during execution and can only store scalar values.
Scalar values are also called primitive values, which includes:
string, number, boolean, null.Constants are defined using the define($name, $value) function.
PHP Constants Example
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PHP Constants Naming Convension
Unlike variables, PHP Constants do not need to start with the dollar sign($). Constants once defined cannot be changed during compile time. Constants are widely written in uppercase and must start with either a letter or an underscore.
PHP Constants Naming Convention Example
PHP defined() Function
defined(string $constantName):bool is a function that checks if a constant exists. It only applies to constants unlike isset() which can be used to check if a variable exists It returns true if a constant is already defined or false if it does not.
PHP Constants defined() Function
What You Should Know at the End of This Lesson
- You should know how to define a PHP constant.
- You should how the PHP constant naming convention works.
- You should know how to check if a constant exists with
defined().