What are common issues with defining and using constants in PHP?

One common issue with defining constants in PHP is that they cannot be changed or redefined once they are set, which can be problematic if you need to update a constant value dynamically. To solve this, you can use the `defined()` function to check if a constant is already defined before defining it again. 

if (!defined('MY_CONSTANT')) {
    define('MY_CONSTANT', 'my_value');
}

Keywords

constant define scope naming conventions redefinition

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