What are the best practices for passing variables between PHP functions using arguments or return statements?

When passing variables between PHP functions, it is generally recommended to use arguments to pass values into a function and return statements to pass values out of a function. This helps to keep the code clean, organized, and easy to understand. By passing variables as arguments, you can explicitly see what values are being used by a function, and by using return statements, you can easily retrieve the result of a function.

// Using arguments to pass variables into a function
function addNumbers($num1, $num2) {
    return $num1 + $num2;
}

$result = addNumbers(5, 10);
echo $result; // Output: 15