What function is used to define constants in php

The define() function is used in PHP to define constants, and its syntax is define($name, $value, $case_insensitive). Parameters include the constant name $name, the value $value, and the case-sensitive $case_insensitive (defaults to false). Constants cannot be reassigned and the name must start with a letter or underscore. They can be referenced within a class using the :: operator. Resolution occurs at compile time.

Function to define constants in PHP

define() function is used in PHP to Define constants.

Syntax

<code class="php">define(string $name, mixed $value, bool $case_insensitive = false);</code>

Parameters

• $name: The name of the constant.
• $value: The value of the constant.
• $case_insensitive: Optional parameter, specifies whether the constant name is case-sensitive. Default is false (case sensitive).

Return value

true, if the constant definition is successful; otherwise, false.

Example

<code class="php">// 定义常量，区分大小写
define('MY_CONSTANT', 'value');

// 定义常量，不区分大小写
define('My_CONSTANT', 'value', true);</code>

Features

##Constant values ​​cannot be reassigned after they are defined.
• Constant names must start with letters or underscores, and can be followed by letters, numbers, or underscores.
• Constant names are case-sensitive unless the
• $case_insensitive parameter is specified as true.
Constants can be referenced within a class using the
• :: operator.
Constants are resolved at compile time and therefore cannot contain any dynamic values.

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