PHP关于数据的舍入归类：round、ceil、floor、number_format

下面是关于数字转化的几种方法：

round -- 对浮点数进行四舍五入

例子：

<?php
echo round(3.4);         // 3

echo round(3.6);         // 4

echo round(3.6, 0);      // 4

echo round(1.95583, 2);  // 1.96

echo round(1241757, -3); // 1242000

echo round(5.055, 2);    // 5.06

?>

ceil -- 进一法取整

例子：

<?php
echo ceil(4.3);    // 5

echo ceil(9.999);  // 10

?>

floor -- 舍去法取整，跟ceil刚刚相反

例子：

<?php
echo floor(4.3);   // 4

echo floor(9.999); // 9
?>

number_format -- 格式化数字为千分位

<?php

$number = 1234;

// english notation (default)
$english_format_number = number_format($number);
echo "First:".$english_format_number."<br />";

// French notation
$nombre_format_francais = number_format($number, 2, ',', ' ');
echo "Second:".$nombre_format_francais."<br />";

// French notation
$number = 1234.564;
$nombre_format_francais = number_format($number, 2, ',', ' ');
echo "Third:".$nombre_format_francais."<br />";

$number = 1234.5678;

// english notation without thousands seperator
$english_format_number = number_format($number, 2, '.', '');
echo "Forth:".$english_format_number."<br />";

?>

显示结果最终如下：
First:1,234
Second:1234,00
Third:1234,56
Forth:1234.57