Due to the precision of the PHP floating point calculation, the order amount is often less than 1 point, and the order is less than 1

Due to the precision of the PHP floating point calculation, the order amount is often less than 1 point, and the order is less than 1

Recently, I encountered a strange problem: the mall often pays less than a penny for the Order, which was caused by the precision of the PHP floating point operation.

It is caused by the precision of the PHP floating point operation. Bolg of laruence has a detailed description. Http://www.laruence.com/2013/03/26/2884.html,
When decimal places are expressed in binary, 0.58 is an infinitely long value for binary.

The binary representation of 0.58 is basically (52 bits): the binary representation of 0010100011110101110000101000111101011100001010001111 is basically (52 bits): 0.57

Convert to a floating point number (64-bit dual-precision)

0.58-> 0.57999999999999996 0.57-> 0.56999999999999995

0.58*100 = 57.999999999 (int) (0.58*100) = 57

Solution:

(Int) (0.58*1000)/10) = 58