$num = 10.4588;
    //第一种：利用round()对浮点数进行四舍五入
    echo round($num,2); //10.46
     
    //第二种：利用sprintf格式化字符串 推荐使用第二种  如果$num = 10 输出$num = 10.00 
    $format_num = sprintf("%.2f",$num);
    echo $format_num; //10.46
     
    //第三种：利用千位分组来格式化数字的函数number_format()
    echo number_format($num, 2); //10.46

    echo number_format($num, 2, '.', ''); //10.46