Why is it important to define constants properly in PHP scripts to avoid unexpected behavior?

Defining constants properly in PHP scripts is important to avoid unexpected behavior because constants are immutable and should not be changed once defined. If constants are not defined correctly, it can lead to errors or unintended changes in the code. To ensure proper definition of constants, use the define() function with the correct syntax and naming conventions.

define('PI', 3.14);
define('DB_NAME', 'my_database');
define('API_KEY', 'my_secret_key');