Fixed a bug that caused errors with the magnitude method when the number was a power of ten.

I fixed it using log10 instead than log(#, 10), and removing $base argument from magnitude method.
Although var_dump(log10(1000)) = double(3) and var_dump(log(1000,10) = double(3), applying floor to the former
results in a "3", as expected, to the latter a "2". Another php wtf?