Summarizing the considerations of numerical calculation in PHP _php tips

One: Rounding

1.round-the floating-point numbers

Float round (float $val [, int $precision])

2:floor-the method of rounding (rounding down)

Float Floor (float $value)

3.ceil-in one method (rounding up)

float ceil (float $value)

Pit point: When the value is an integer for example 11 floor (one) = ten, ceil (11) = 12; The problem is obvious, so be careful when calculating

Solution: Floor (11 + 0.01);

Two: integer and decimal multiplication apart

Pit Point:3.5 * 100 = 300, even if you are not good at math, in the PHP world This is the truth, if you use PHP's +-*/to calculate floating-point numbers, you may encounter some problems of computational error, such as Echo intval (0.58*100); Will print 57 instead of 58, which is actually a bug in the bottom of the computer that cannot accurately represent floating-point numbers, which is cross-language, and I've encountered this problem with Python. So basically most languages provide a class library or function library for accurate computing, such as PHP with a high accuracy function library of BC

Workaround: change the integer form to floating-point 3.5 * (float) 100 = 350

Three: The oddity of floating point numbers

Pit point:8.50–8 = 0.500000001 In fact, the reason is almost 2.

Solution: round the result () and improve the precision

Summarize

The above is the PHP data calculation of the full contents of the note, I hope this article in the content of PHP in the data calculation can be helpful.