Make var_dump() use serialize_precision

Hi internals, https://github.com/php/php-src/pull/5172 changes var_dump() to use serialize_precision instead of precision to dump floating-point numbers. To recap: serialize_precision defaults to -1, which will print exactly as many floating-point digits as are needed to represent the number accurately. precision defaults to 14, which will print a shorter but potentially inaccurate float representation. The motivation here is that var_dump() is debugging functionality and should print values as accurately as possible. The single most common bug report we receive is some kind of variation on: $sum = 0.1 + 0.2; var_dump($sum); // float(0.3) var_dump($sum == 0.3); // bool(false) WTF??? After this change, this would instead be: $sum = 0.1 + 0.2; var_dump($sum); // float(0.30000000000000004) var_dump($sum == 0.3); // bool(false) Makes sense... I have little hope that developers will suddenly start understanding floating-point numbers, but at least this should reduce the amount of confusion. Does anyone see an issue with doing this change? Regards, Nikita