PHP中round()函数对浮点数进行四舍五入的方法

本文实例讲述了PHP中round()函数对浮点数进行四舍五入的方法。分享给大家供大家参考。具体方法如下：

语法:round(x,prec)

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,实例代码如下:

<?php
*/
echo round(3.4);         //输出3
echo "<br>";
echo round(3.5);         //输出4
echo "<br>";
echo round(3.6);         //输出4
echo "<br>";
echo round(3.6,0);         //输出4
echo "<br>";
echo round(1.95583,2);        //输出1.96
echo "<br>";
echo round(1241757,-3);        //输出1242000
echo "<br>";
echo round(4.045,2);         //输出4.05
echo "<br>";
echo round(4.055,2);         //输出4.06
 
//使用stdround函数代替php的round函数
?>

<?php
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 ";
?>

希望本文所述对大家的PHP程序设计有所帮助。