How to define constants in php?

As we all know, constants are the same as <span style="font-family:monospace">variables</span>, both are used to save data.

1. The basic concept of constants

const/constant: It is an unchangeable quantity (data) during the running of the program;

final modifier. (About the final modifier "Final's Journey in this Life")

2. The form of constant definition

define ('constant name', constant value)

<?php
   define(&#39;A&#39;,10);
   echo A;
?>

constKeyword

<?php
  const A=10;
   echo A;
?>

3. Naming of constants Rules

• # Constants do not need to use the "$" symbol, once used they are considered variables.

• Variable names can be named by numbers, letters, and underscores, but they must start with letters and underscores.

• The names of constants are usually in uppercase letters (to distinguish them from variables).

• The rules for variable naming are looser than variables, and some special characters (define function) can be used.

• Variables are usually not case-sensitive, but they can be (the third parameter of the define function).

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