php 高精度计算

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bcadd -- Add two arbitrary precision numbers

bcsub -- Subtract one arbitrary precision number from another

bccomp -- Compare two arbitrary precision numbers
bcdiv -- Divide two arbitrary precision numbers
bcmod -- Get modulus of an arbitrary precision number
bcmul -- Multiply two arbitrary precision number
bcpow -- Raise an arbitrary precision number to another
bcpowmod -- Raise an arbitrary precision number to another, reduced by a specified modulus
bcscale -- Set default scale parameter for all bc math functions
bcsqrt -- Get the square root of an arbitrary precision number
bcsub -- Subtract one arbitrary precision number from anothe