The use of define and defined in php

For some fixed quantities in php, we often use constants to store them, so how to define constants? How to judge after defining it? This article will take you to take a look.

1. Use define to define a constant

<?php

 define ("PATH","/zend/php/define.php");
 echo PATH;
?>

2. Use defined to determine whether the constant exists

<?php
 define ("PATH","/zend/php/define.php");
 echo PATH."<br>";

 if(defined(&#39;PATH&#39;)){
    echo &#39;PATH&#39;."存在";
 }
?>

输出：/zend/php/define.php
      PATH存在

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