How to implement constant array in php? Introduction to how to define array constants in php

Constants are quantities that cannot be changed. The define and const keywords are used in PHP to define constants. The following article will introduce to you how to define array constants in PHP. Let's take a look at the specific content.

Let’s take a brief look at define and const

define is a Universal constants used everywhere.

Because define has the characteristics of global scope, even if it is defined in a function, it also has the characteristics of being able to be referenced outside the function. If the function is executed again, a double definition error will occur, so it is usually defined outside the function.

const is used to define constants as members of class. This is a static member of the class, described as classname::constname.

Let’s take a look atThe basic method of defining a constant array

define('常量数组名1', ['值1', '键2' => '值2']);   // 常量数组的定义
echo 常量数组名1['键2'];  // 常量数组元素的参考
foreach (常量数组名1 as $value) {   // 使用循环
    echo $value;
}
class 类名
{
    const 常量数组名2 = ['值3', '键4' => '值4'];  // 常量数组的定义
}
echo 类名::常量数组名2['键4'];    // 常量数组元素的参考
foreach (类名::常量数组名2 as $value) { // 使用循环
    echo $value;
}

Let’s take a look at a specific example

The code is as follows

<?php
define(&#39;STATUS&#39;, [100=>&#39;未请求&#39;,200=>&#39;请求确认付款&#39;,300=>&#39;确认收款&#39;]);
class Prefecture
{
    const NAMES = [&#39;合肥&#39;,&#39;南京&#39;,&#39;上海&#39;,&#39;杭州&#39;];

    public function show($id)
    {
        echo self::NAMES[$id], PHP_EOL;
    }
}
print_r(STATUS);
echo STATUS[200], PHP_EOL;
print_r(Prefecture::NAMES);
echo Prefecture::NAMES[0], PHP_EOL;
$prefecture = new Prefecture;
$prefecture->show(2);

The execution results are as follows

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