PHP 格式化输出

$format = 'The %2$s contains %1$04d monkeys! %s apples.';
echo sprintf($format, 4, 'tree');
// output: The tree contains 0004 monkeys! 4 apples.

// number_format(数字, 保留小数位数, 小数分割符='.', 千分位分隔符=',');
$num = 1234.567;
echo number_format($num); // 1,235
echo number_format($num, 2); // 1,234.57
echo number_format($num, 2, '.', ''); // 1234.57
echo number_format($num, 2, '_', ','); // 1,234_57