Issue while adding the numbers in PHP [duplicate]

Question

Adding two numbers in PHP getting unexpected results, such as this

$a=115.40;
$b=120.25;
$c=4.85;
echo ($a-$b)+$c;

results in

-5.3290705182008E-15

these numbers maybe integers or floats

Due to the nature of how folating-points works in computing in general, they are not going to be exactly the result you expect. What you're seeing now is that the floating-point is about zero, but not exactly zero. You can format it to be zero, example: 3v4l.org/P70iL — Qirel
– Qirel, Commented May 12, 2017 at 13:24

Alon Eitan · Accepted Answer · 2017-05-12 13:19:07Z

0

If you add floats, you can have solutions like that. Please check Manual:

Additionally, rational numbers that are exactly representable as floating point numbers in base 10, like 0.1 or 0.7, do not have an exact representation as floating point numbers in base 2, which is used internally, no matter the size of the mantissa. Hence, they cannot be converted into their internal binary counterparts without a small loss of precision. This can lead to confusing results: for example, floor((0.1+0.7)*10) will usually return 7 instead of the expected 8, since the internal representation will be something like 7.9999999999999991118....

edited May 12, 2017 at 13:19

Alon Eitan

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answered May 12, 2017 at 13:18

timiTao

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