F1:四舍五入保留两位小数，不补齐0
echo round($num,2);
F2:不四舍五入保留两位小数，不补齐0
echo floor($num*10000)/100);
F3:保留两位小数，自动补齐0，直接截取
echo sprintf(“%.2f”, $num);
F4:四舍五入，保留两位小数，自动补齐0
sprintf(“%.2f”, round($n,2));
F5:不四舍五入，保留两位小数，自动补齐0
echo sprintf(“%.2f”,floor($num*10000)/100);