Detailed explanation of the difference between define and const in php

Everyone should know that define and const are constants in PHP, but how much do you know about them? This article mainly shares with you a detailed explanation of the difference between define and const in PHP, hoping to help everyone.

Understanding of constants:

1. There is no dollar sign ($) in front of the constants;

2. Constants can only be used define() function definition, not through assignment statements;

3. Constants can be defined and accessed anywhere regardless of the scope of the variable;

4. Once defined, a constant cannot be redefined or undefined;

5. The value of a constant can only be a scalar.

The difference between constant definitions:

Use of const	Use of define
const is used for the definition of class constants	Define cannot be used for the definition of class constants, but can be used for global constants.
You cannot use const to define constants within functions, loops, and if statements.	define can use an ordinary constant name
const	define can use an expression as the name
const can only accept static scalars	define can use any expression
const-defined constants are case-sensitive	define can use the first Three parameters (true indicates case insensitivity) to specify whether case sensitivity is present.

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