Why is it recommended to avoid modifying PHP files at runtime, especially for constants?

Modifying PHP files at runtime, especially for constants, can lead to unexpected behavior and errors in your application. Constants are meant to be defined once and remain unchanged throughout the execution of the script. If you need to change a constant value, it's better to define it in a configuration file and include that file in your script. This way, you can easily update the constant value without modifying the PHP file directly. 

// config.php
define('MY_CONSTANT', 'initial_value');

// index.php
include 'config.php';
echo MY_CONSTANT; // initial_value

// To update the constant value
define('MY_CONSTANT', 'new_value');
echo MY_CONSTANT; // new_value

Keywords

PHP runtime modifying constants recommended

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