PHP关于数据的舍入关键字归类：round() ceil() floor() number_format()

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