In PHP, the ______ function checks if a constant with a given name exists.

In PHP, the defined() function checks if a constant with a given name exists. It takes a constant name as an argument and returns true if the constant is defined, and false otherwise. This function is useful when you need to determine if a constant has been defined before accessing its value to avoid potential errors. Using the defined() function helps ensure that you are working with valid and defined constants. Learn more: https://www.php.net/manual/en/function.defined.php