如何根据区间进行判断？

function findLevel($val)

{

    $arr = [0,10,15,20,25,100];



    $feedback = [

            '0-1' => '大于等于0°小于10°',

            '1-2' => '大于等于10°小于15°',

            '2-3' => '大于等于15°小于20°',

            '3-4' => '大于等于20°小于25°',

            '4-5' => '大于等于25°小于100°'

        ];



    $l = count($arr);

    $low = 0;

    $high = $l -1;



    if($arr[$low] > $val)

    {

        return '输入值小于最小值';

    }



    if($arr[$high] < $val)

    {

        return '输入值大于最大值';

    }



    $dValue = $high - $low;

    while($dValue != 1)

    {

        $middle = floor(($low + $high) / 2);

        if($arr[$middle] > $val)

        {

            $high = $middle;

        }

        else

        {

            $low = $middle;

        }

        $dValue = $high - $low;

    }



    $index = $low . '-' . $high;



    return $feedback[$index];

}



    

echo findLevel(14);

echo findLevel(15);

echo findLevel(16);

    $middle = floor(($low + $high) / 2);

    if($arr[$middle] == $val)

    {

        return $middle;

    }

        elseif($arr[$middle] > $val)

    {

        $high = $middle - 1;

    }

    else

    {

        $low = $middle + 1;

    }