What are the best practices for passing variables to and from PHP functions?

When passing variables to and from PHP functions, it is important to use parameters to pass data into a function and return statements to send data back. To pass variables into a function, you can define parameters within the function declaration. To return data from a function, use the return statement to send the data back to where the function was called.

// Passing variables to a PHP function
function addNumbers($num1, $num2) {
    $sum = $num1 + $num2;
    return $sum;
}

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