php 按最大尺度 等比例缩放图片

		    	$maxWidth = 180;//最大宽度
		    	$maxHeight = 125;   //最大高度 
	
		        $iSuofang = $arrPicwh['w']/$arrPicwh['h'];//原图的比例
		        $iSuo = $arrPicwh['h']/$arrPicwh['w'];
		        if ($arrPicwh['w'] > $arrPicwh['h'])//判断原图的宽高那个大
		        {
		        	$dstW = $maxWidth;
		        	$dstH = $maxWidth * $iSuo;
		        }else 
		        {
		        	$dstH = $maxHeight;
		        	$dstW = $maxHeight * $iSuofang;
		        	
		        }