Function to convert a value in a range to an equivalent value in a different range.

rangeConverter.php

<?php

function rangeConverter(
    int $input,
    int $inputRangeMin,
    int $inputRangeMax,
    int $outputRangeMin = 0,
    int $outputRangeMax = 100
) :int
{
    if ($inputRangeMax <= $inputRangeMin) {
        throw new \http\Exception\InvalidArgumentException('$inputRangeMax must be greater than $inputRangeMin');
    }
    if ($outputRangeMax <= $outputRangeMin) {
        throw new \http\Exception\InvalidArgumentException('$outputRangeMax must be greater than $outputRangeMin');
    }

    if ($input < $inputRangeMin) {
        throw new \http\Exception\InvalidArgumentException('$input must be greater than $inputRangeMin');
    }
    if ($input > $inputRangeMax) {
        throw new \http\Exception\InvalidArgumentException('$input must be less than $inputRangeMax');
    }

    return (
        ($outputRangeMax - $outputRangeMin)
        *
            (
                ($input - $inputRangeMin)
                /
                ($inputRangeMax - $inputRangeMin)
            )
        )
        +
        $outputRangeMin;
}