For php 7 compatibility we use `(double)'1E3'` now and compare it to
rounded value now. This should be faster and is compatible to php 7 and
upward.

Since php 7.1 `(int)'1E3'` returns 1000 - same as `(double)'1E3'`. Before
`(int)'1E3'` returned 1 what is wrong.

Because the manual calculation is not necessary since php 7.1 we skip it
for php >= 70100.

Error object (solves #1)