例1，格式化数字为文本
例2，number_format($n, $p, $t, $d) rounds $n to $p decimal places, using $t as the thousands separator and $d as the decimal separator.
例3，number_format函数用于English format and Italian format
<?php
$a = 1232322210.44;
echo number_format ($a, 2); // English format
echo "n";
echo number_format ($a, 2, ',', '.'); // Italian format
echo "n";
?>
例4，输出格式化的数字形式