PHP: rfc:base_convert_improvements

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====== PHP RFC: base_convert changes ======
  * Version: 0.1
  * Date: 2019-05-15
  * Author: Scott Dutton,php@exussum.co.uk
  * Status: Implemented (in PHP 7.4)
  * First Published at: https://wiki.php.net/rfc/base_convert_improvements



===== Introduction =====
The base_convert family of functions(base_convert, binhex, hexbin etc) are very accepting with their input arguments, you can pass any string to to them and they give a best effort of converting it.

For example base_convert("hello world", 16, 10); will return 237 with no warnings. What this does internally is base_convert("ed", 16, 10); 

Also negative numbers simply do not work, eg base_convert("-ff", 16, 10); will return 255. (similar to above the "-" gets silently ignored).

Experienced developers get caught out by this for example  https://gist.github.com/iansltx/4820b02ab276c3306314daaa41573445#file-getlines-php-L9

In this case literal binary data was the input and the result was 0 (which is expected but not clear)

Other functions affected by this are:

  * decbin() - Decimal to binary
  * bindec() - Binary to decimal
  * decoct() - Decimal to octal
  * octdec() - Octal to decimal
  * dechex() - Decimal to hexadecimal
  * hexdec() - Hexadecimal to decimal



Other programming languages behave in a a similar way to this proposal
 * Javascript - https://jsfiddle.net/c16b4usp/
 * Python - https://repl.it/repls/OliveBlushingModem
 * Go - https://play.golang.org/p/aLWg15c00Fy

Javascript does work with larger numbers correctly, Python and Go work in a way which would be similar to PHP if this change was made.



===== Proposal =====
I propose two changes to the base_convert family of functions. 

=== Error on ignored characters ===
When passed arguments that base_convert will ignore, also give a warning to the user informing them their input was incorrect.
There is an exception in place for the second char, if base is 16 'x' is allowed eg "0xff", base 2 allows b and base 8 allows o. this fits in with common formats for these numbers 


This can be raised to a full exception for a later PHP version (eg PHP 8)

=== Allow negative arguments ===
Negative numbers should be allowed to be passed to the base_convert family of functions. for example base_convert('-ff', 16', 10); should return -255. Currently users need to make an exception in this case


===== Backward Incompatible Changes =====
=== Error on ignored characters ===
No BC breaks for a warning, in the case of an exception there will be a BC break - Would suggest PHP 8 for this.

=== Allow negative arguments ===
base_convert currently in the backend has a zend_ulong as its representation. We would need a zend_long. This will change the behavior of numbers in the range 9223372036854775807 - 18446744073709551615 but will allow negative numbers.

This currently breaks a fair amount of unit tests that I will need to update if this change is accepted.  The unit tests are around extreme values.

A secondary BC change would be people who have worked around this in userland code for example

https://stackoverflow.com/a/7051224/1281385

This change will break these work arounds

Would suggest PHP8 for this change


===== Proposed PHP Version(s) =====
PHP 7.4 for warnings
PHP 8.0 for negative arguments and exceptions

===== RFC Impact =====
==== To SAPIs ====
None

==== To Existing Extensions ====
None

==== To Opcache ====
None

==== New Constants ====
None

==== php.ini Defaults ====


===== Open Issues =====
Make sure there are no open issues when the vote starts!

===== Unaffected PHP Functionality =====
Only the base_convert family of functions will be changed

===== Future Scope =====
Allow base_convert to allow any length input and not be restricted to a 64 bit int type

===== Proposed Voting Choices =====
2 votes
=== Error on ignored characters ===
This vote will be to raise a E_DEPRECATED warning for PHP 7.4. Raising to be an InvalidArgumentException in PHP 8

=== Allow negative arguments ===
This vote will allow negative arguments in PHP 8

===== Patches and Tests =====
https://github.com/php/php-src/pull/3911


===== Vote =====
Started 19th June 2019. Ends 3rd July 2019
<doodle title="Raise deprecated error in 7.4 and raise to exception in PHP 8 for unknown characters" auth="exussum" voteType="single" closed="true">
   * Yes
   * No
</doodle>

<doodle title="Allow negative numbers to be converted in PHP 8" auth="exussum" voteType="single" closed="true">
   * Yes
   * No
</doodle>
===== References =====
https://bugs.php.net/bug.php?id=61740
https://bugs.php.net/bug.php?id=55393

===== Rejected Features =====
Keep this updated with features that were discussed on the mail lists.
Page Tools
