What does php defined mean?

php defined is a function used to define a constant in PHP. Its usage syntax is "define(name, value, case_insensitive)", and its parameter name specifies the name of the constant.

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

What does php defined mean?

define() function defines a constant.

Constants are similar to variables, except that:

After setting, the value of the constant cannot be changed

Constant names do not require a dollar sign ($) at the beginning

Scope does not affect access to constants

Constant values ​​can only be strings or numbers

Syntax

define(name,value,case_insensitive)

Parameters

name required . Specifies the name of the constant.

value Required. Specifies the value of the constant.

case_insensitive

Optional. Specifies whether constant names are case-sensitive.

If set to true, it will not be case sensitive. Default is false (case sensitive).

Example

Define a case-sensitive constant:

<?php
define("GREETING","Hello world!");
echo constant("GREETING");
?>

Output:

Hello world!

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