求指教一个区间查值的问题

 if($bbb>0&&$bbb<=100){$baifen=100;}            elseif($bbb>100&&$bbb<=500){$baifen=500;}            elseif($bbb>500&&$bbb<=1000){$baifen=1000;}            elseif($bbb>1000&&$bbb<=5000){$baifen=5000;}

$arr[0,100,500,1000,5000];$b[100,500,1000,5000];

function binarysearch($array,$value){		//起始位置，你可以作为函数参数		$low = 0;		$high = count($array)-1;		while($low <= $high){			$mid = ceil(($low+$high)/2);			if($array[$mid] == $value)				return $mid;			if($array[$mid] < $value){				$low = $mid + 1;			}			if($array[$mid] > $value){				$high = $mid - 1;			}		}		return -1;	}

if($bbb > 1000) ) $baifen = 5000;elseif($bbb > 500) $baifen = 1000;elseif($bbb > 100) $baifen = 500;elseif($bbb > 0) $baifen = 100;

$dict = array(0 => 100, 100 => 500, 500 => 1000, 1000 => 5000);krsort($dict);foreach($$dict as $k=>$v) if($x > $k) break;echo $v;

if($bbb > 1000) ) $baifen = 5000;elseif($bbb > 500) $baifen = 1000;elseif($bbb > 100) $baifen = 500;elseif($bbb > 0) $baifen = 100;

$dict = array(0 => 100, 100 => 500, 500 => 1000, 1000 => 5000);krsort($dict);foreach($$dict as $k=>$v) if($x > $k) break;echo $v;