PHP RFC: Raising zero to the power of negative number

• Version: 1.0
• Date: 2024-01-11
• Author: Jorg Sowa jorg.sowa@gmail.com
• Status: Draft
• First Published at: http://wiki.php.net/rfc/raising_zero_to_power_of_negative_number

Raising a number to the power of a negative number is equivalent to taking the reciprocal of the number raised to the positive opposite of the power.

If we raise the number zero to the power of a negative number we end up with the one divided by zero, which gives an undefined result. Currently in PHP, such operation results in `INF`, while explicit division by zero gives a DivisionByZeroError.

var_dump(0 ** -1); //float(INF)
 
var_dump(pow(0,-1)); //float(INF)
 
var_dump(1/0); //DivisionByZeroError: Division by zero

The RFC proposes to change the behavior of this operation to match the division by zero operation. In the next minor version such an operation will throw a Deprecation notice, and for the major version, this operation will throw DivisionByZeroError.

This change will break all code including raising the zero number to a negative power.

Deprecation Notice in the next minor PHP version 8.4.

Throwing DivisionByZeroError in the next major PHP version: 9.0.

As per the voting RFC, a yes/no vote with a 2/3 majority is needed for this proposal to be accepted.

Voting started 2024-x-x and closed 2024-x-x.

https://github.com/jorgsowa/php-src/pull/11

The implementation is based on Ilija Tovilo's PoC: https://github.com/php/php-src/issues/8015#issuecomment-1193391843

Issue GH-8015: https://github.com/php/php-src/issues/8015