Get values of default arguments based on previous argument

Question

I have a PHP function that takes three arguments, where one is an optional argument.

function theRange($min, $max) {
    // Function Body
}

But I have to set the limit to a default parameter and give it as an optional parameter. So, what I did is:

function theRange($min, $max = 5) {
    // Function Body
}

The problem comes when the $min is greater than 5 and the value becomes invalid if the maximum is lesser the the minimum value. So, I default the $max to $min, so what I did is:

function theRange($min, $max = $min) {
    // Function Body
}

This throws an error as below:

Parse error: syntax error, unexpected '$min' (T_VARIABLE) in functions.php on line 2.

I am currently handling it this way:

function theRange($min, $max = null) {
    if (!isset($max) || is_null($max))
         $max = $min;
    // Function Body
}

Is there a better way to handle this default parameter, to have the previous parameter as an input scenario? Thanks in advance! :)

Answer 1

Simply assign default value, and check if it's valid inside function:

function theRange($min, $max = 5) {
    $max = $min > $max ? $min : $max;
}