Fix INF/NAN to string rendering

[bilhackmac]

INF / -INF / NAN are not always rendered as desired when transformed to string using number_format and printf.

echo number_format(INF), ' @ ', number_format(-INF), ' @ ', number_format(NAN);
# inf @ inf @ nan
// => Missing minus sign on second inf


printf('%f @ %f @ %f', INF, -INF, NAN);
# INF @ INF @ NaN
// => Missing minus sign on second INF
// => NaN is inconsistant with other 'not a number' rendering (nan or NAN)

printf('%+f', INF);
# INF
// => Missing plus sign before INF

printf('%+0f', INF);
printf('%+0f', -INF);
printf('%+0f', NAN);
# +NF
# -NF
# +aN
// => Buggy

printf('@%10f@', INF);
printf('@%-10f@', INF);
# @INF@
# @INF@
// => No right or left padding

This PR fix these cases

[Girgias]

Somewhat related to #9209/#10201

[bilhackmac]

No I see these issue and PR before but it's not related

[Girgias]

No I see these issue and PR before but it's not related

I said "somewhat" related. I know full well that this is not the same issue as in that issue/PR, but it's a similar issue enough that it probably indicates there is a larger problem at stake here in with how we handle these cases across the codebase.

[bilhackmac]

Any progress on this problem ?

[marc-mabe]

For the case of number_format wouldn't it make more sense to match what NumberFormatter is returning for [-]INF ?

$ php -r 'var_dump((new NumberFormatter("en_US", NumberFormatter::DECIMAL))->format(INF));'
string(3) "∞"

$ php -r 'var_dump((new NumberFormatter("en_US", NumberFormatter::DECIMAL))->format(-INF));'
string(4) "-∞"

$ php -r 'var_dump((new NumberFormatter("en_US", NumberFormatter::DECIMAL))->format(NAN));'
string(3) "NaN"

[bilhackmac]

It make sense for me but this small change can have large impact and should be discussed by core PHP team