How to set constants in php

How to set constants in php: 1. Use the define() function, the syntax "define('constant name', 'constant value')"; 2. Use the const keyword, the syntax "const constant name = constant value;".

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

The so-called constant is a quantity that cannot be changed, in PHP Once a constant is defined, it cannot be modified or undefined.

PHP constants are usually used to store data that does not change and is not expected to change. The data can only be data of four scalar data types: integer, floating point, string, and Boolean. However, Starting from PHP7, constants support array types.

How to set constants

1. Use the define() function

Legal constants A name can only begin with a letter and an underscore, and can be followed by any length of letters, numbers, or underscores. In PHP, you can define a constant through the define() function. The syntax of the define() function is as follows:

define(string $name, mixed $value [, bool $case_insensitive = false])

define() The description of the function parameters is as shown in the following table:

Parameters	Description
$name	Required parameter, constant name (needs to be wrapped in double quotes or single quotes)
$value	Required parameter, constant value
$case_insensitive	Optional parameter, Specify whether to be case-sensitive. The default is case-sensitive. If set to true, it means case-insensitive

2. Use the const keyword

In addition to using the define() function, you can also use the const keyword to define constants. The syntax of the const keyword is as follows:

const 常量名 = 常量值;

The following uses examples to demonstrate the use of constants:

<?php
header("Content-type:text/html;charset=utf-8");
define(&#39;WebSite&#39;, &#39;php中文网&#39;);
const url = &#39;https://www.php.cn/&#39;;
echo WebSite.&#39;<br>&#39;;
echo url;
?>

Running results:

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