How to use php define function

php define function is used to define a constant. Its syntax is define(name, value, case_insensitive). The parameter name is required and specifies the name of the constant; value is required and specifies the value of the constant.

#How to use the php define function?

Definition and usage

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 and numbers

Syntax

define(name,value,case_insensitive)

Parameters

name is required. Specifies the name of the constant.

value Required. Specifies the value of the constant. PHP7 supports arrays, examples are as follows:

<?php
// PHP7+ 支持
define(&#39;ANIMALS&#39;, [
    &#39;dog&#39;,
    &#39;cat&#39;,
    &#39;bird&#39;
]);
echo ANIMALS[1]; // 输出 "cat"
?>

case_insensitive Optional. Specifies whether constant names are case-sensitive. Possible values:

TRUE - case insensitive

FALSE - default. Case sensitive

Return value:

Returns TRUE if successful, returns FALSE if failed.

PHP Version: 4

Example 1

Define a case-insensitive constant:

<?php 
define("GREETING","Hello you! How are you today?",TRUE); 
echo constant("greeting"); 
?>

Output:

Hello you! How are you today?

Example 2

Define a case-sensitive constant:

<?php 
define("GREETING","Hello you! How are you today?"); 
echo constant("GREETING"); 
?>

Output:

Hello you! How are you today?

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