PHP - GMP and floating point numbers?

The following code outputs 0, which isn't correct:

$r = gmp_pow(gmp_init('-1.7976931348623157'), 308);
echo开发者_运维知识库 gmp_strval($r);

I was under the impression that the GMP library was capable of handling floating point numbers, or have I made a mistake in the code?

GMP library was capable of handling floating point numbers,

It's not. You can test that with:

echo gmp_strval(gmp_init('18')); // 18
echo gmp_strval(gmp_init('1.8')); // 0

Now, what you could do is use BCMath instead:

$num = bcpow('-1.7976931348623157', '308');
echo $num;
echo floatval($num); // for a "prettier" format