round() 函数对浮点数进行四舍五入

语法
round(x,prec)参数 描述
x 可选。规定要舍入的数字。
prec 可选。规定小数点后的位数。

说明
返回将 x 根据指定精度 prec （十进制小数点后数字的数目）进行四舍五入的结果。prec 也可以是负数或零（默认值）。
提示和注释
注释：php教程 默认不能正确处理类似 "12,300.2" 的字符串。

注释：prec 参数是在 php 4 中被引入的。。

*/
echo round(3.4);         //输出3
echo "
";
echo round(3.5);         //输出4
echo "
";
echo round(3.6);         //输出4
echo "
";
echo round(3.6,0);         //输出4
echo "
";
echo round(1.95583,2);        //输出1.96
echo "
";
echo round(1241757,-3);        //输出1242000
echo "
";
echo round(4.045,2);         //输出4.05
echo "
";
echo round(4.055,2);         //输出4.06

//使用stdround函数代替php的round函数
?>

    function   stdround($num,   $d=0)
    {
      return   round($num   +   0.0001   /   pow(10,   $d),   $d);
    }  
       
echo   "round(1.005,2)= ".round(1.005,2). "n ";
echo   "round(1.015,2)= ".round(1.015,2). "n ";
echo   "round(1.025,2)= ".round(1.025,2). "n ";
echo   "round(1.035,2)= ".round(1.035,2). "n ";
echo   "round(1.045,2)= ".round(1.045,2). "n ";
echo   "round(1.055,2)= ".round(1.055,2). "n ";
echo   "round(1.065,2)= ".round(1.065,2). "n ";
echo   "round(1.075,2)= ".round(1.075,2). "n ";
echo   "round(1.085,2)= ".round(1.085,2). "n ";
echo   "round(1.095,2)= ".round(1.095,2). "n ";

echo   "stdround(1.005,2)= ".stdround(1.005,2). "n ";
echo   "stdround(1.015,2)= ".stdround(1.015,2). "n ";
echo   "stdround(1.025,2)= ".stdround(1.025,2). "n ";
echo   "stdround(1.035,2)= ".stdround(1.035,2). "n ";
echo   "stdround(1.045,2)= ".stdround(1.045,2). "n ";
echo   "stdround(1.055,2)= ".stdround(1.055,2). "n ";
echo   "stdround(1.065,2)= ".stdround(1.065,2). "n ";
echo   "stdround(1.075,2)= ".stdround(1.075,2). "n ";
echo   "stdround(1.085,2)= ".stdround(1.085,2). "n ";
echo   "stdround(1.095,2)= ".stdround(1.095,2). "n ";

$m=0.000000000000001;
echo   "n ";
echo   "round(1.005+{$m},2)= ".round(1.005+$m,2). "n ";
echo   "round(1.015+{$m},2)= ".round(1.015+$m,2). "n ";
echo   "round(1.025+{$m},2)= ".round(1.025+$m,2). "n ";
echo   "round(1.035+{$m},2)= ".round(1.035+$m,2). "n ";
echo   "round(1.045+{$m},2)= ".round(1.045+$m,2). "n ";
echo   "round(1.055+{$m},2)= ".round(1.055+$m,2). "n ";
echo   "round(1.065+{$m},2)= ".round(1.065+$m,2). "n ";
echo   "round(1.075+{$m},2)= ".round(1.075+$m,2). "n ";
echo   "round(1.085+{$m},2)= ".round(1.085+$m,2). "n ";
echo   "round(1.095+{$m},2)= ".round(1.095+$m,2). "n ";

echo   "round(1.005,2)= ".round(1.005,2). "n ";
echo   "round(1.015,2)= ".round(1.015,2). "n ";
echo   "round(1.025,2)= ".round(1.025,2). "n ";
echo   "round(1.035,2)= ".round(1.035,2). "n ";
echo   "round(1.045,2)= ".round(1.045,2). "n ";
echo   "round(1.055,2)= ".round(1.055,2). "n ";
echo   "round(1.065,2)= ".round(1.065,2). "n ";
echo   "round(1.075,2)= ".round(1.075,2). "n ";
echo   "round(1.085,2)= ".round(1.085,2). "n ";
echo   "round(1.095,2)= ".round(1.095,2). "n ";