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php Precision calculation problem
Let’s take a look at an interesting phenomenon in PHP: var_dump( intval(0.58 * 100 ) ); Guess what result this code will output?
The output result is 57, not 58
##Why is this? This is all caused by floating point arithmetic.
Actually, these results are not language bugs, but are related to the implementation principle of the language. All numbers in js are unified as Number, including integers, which are actually all double precision (double) types.
##As for 0.58 * 100 We don’t think about the specific multiplication of floating point numbers in detail. We just look at it vaguely with mental arithmetic... 0.58 * 100 = 57.999999999
Then if you intval it, it will naturally be 57...
It can be seen that, The key point of this problem is: "You seem to have a finite decimal, but it is infinite in the binary representation of the computer."
PHP floating point type has inaccuracy in +-*%/
We can solve the problem of inaccurate floating point operations through the following commonly used high-precision functions:bcadd — Add two high-precision numbers
bccomp — Compares two high-precision numbers, returns -1, 0, 1
bcdiv — Divides two high-precision numbers
bcmod — Finds the remainder of a high-precision number
bcmul — Multiply two high-precision numbers
bcpow — Find the power of a high-precision number
bcpowmod — Find the power of a high-precision number and its modulus, very commonly used in number theory
bcscale — Configure the default number of decimal points, which is equivalent to "scale=" in Linux bc
bcsqrt — Find the square root of a high-precision number
bcsub — Concatenate two high-precision numbers reduce
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