Hhvm: php 7 is not the same as php 7.1 or PHP 7.2

[photodude]

HHVM Version 3.12-3.16

Standalone code, or other way to reproduce the problem

Set hhvm to php 7 mode, the behavior is compatible with php 7 but not always with php 7.1

Expected result

• [x] we should have ini options for a php 7 mode
• [ ] we should have an ini option for a php 7.1 mode
  
  
  
  • a number of issues have been opened for php 7.1 compatibility problems with hhvm
  
  

Actual result

We currently have a broken php 7 mode ini option (see #7198), but no php 7.1 mode ini option

A few of PHP 7.1 gotcha's, showing some need for a php 7.1 mode

• DateTime now supports microseconds; will break a lot of code
• Unserialize notices get printed before instead of after __destruct runs
• Casting "NAN", "INF" and "infinity" no longer works
• var_dump recursion detection works like it did before php7
• JSON_PRETTY_PRINT uses less whitespace for indenting
• DateInterval can no longer be accessed as array

[paulbiss]

Is there a reason we shouldn't just update PHP 7 mode to match 7.1? I'd rather not add a new mode for every version of 7, it's hard enough supporting 5, 7, hack, and various combinations thereof.

[photodude]

php 7 is supported until 3 Dec 2018
php 7.1 is expected to be released in January 2017 and supported until 1 Dec 2019
Backward incompatible changes http://php.net/manual/en/migration71.incompatible.php
changed functions http://php.net/manual/en/migration71.changed-functions.php

I'm not sure if I have an opinion on why "we shouldn't just update PHP 7 mode to match 7.1", Especially if it's documented what behavior we should expect from HHVM.

On the other hand, we kind of have a framework in place on how to version the php 7 mode
consider the tag hhvm.php7.all which "fully enables PHP 7 mode" this could be considered "fully enable the most recent PHP 7.x mode" then add other php 7.x compatibility items as follows

SETTING | TYPE | DEFAULT | DESCRIPTION | PHP 7.x RFC
------------ | ------------- | ------------ | ------------- | ------------
hhvm.php7.date_time | bool | hhvm.php7.all | |
hhvm.php7.date_interval | bool | hhvm.php7.all | |
hhvm.php7.unserialize_notices | bool | hhvm.php7.all | |
hhvm.php7.casting | bool | hhvm.php7.all | |
hhvm.php7.var_dump | bool | hhvm.php7.all | |
hhvm.php7.json_pretty_print | bool | hhvm.php7.all | |

[ezzatron]

Another thing to consider here is that PHP 5.6 active support ends in 16 days.

IMO, in light of this, it would be perfectly understandable if HHVM dropped PHP 5 support altogether in the next release. At least then you'd only have 7.0 and 7.1 differences to worry about.

[photodude]

@ezzatron because Security Support for PHP 5.6 will continue until 31 Dec 2018 (about the same point that php 7 Security Support ends) most developers and frameworks are more likely to support php 5.6 than php 7. I think dropping php 5 support from HHVM now would be the wrong choice and would likely reduce HHVM adoption.

[ezzatron]

Fair call, I just thought that perhaps if you want PHP 5 support, you use an older version of HHVM. But I can understand the logic for keeping it in too.

[photodude]

@ezzatron just look at number of php5 incompatibility tags about 246 issues... to see why even the current HHVM doesn't yet fully support PHP 5 code. It's hard to convice projects to use HHVM when there are issues blocking use and adoption.

[photodude]

@mxw please include this in the upcoming meeting on php7

[fredemmott]

https://hhvm.com/blog/2017/09/18/the-future-of-hhvm.html

[photodude]

Thanks for the notification @fredemmott I'll close my other issues for the same reason.

[fredemmott]

To clarify, it’s not that we’re not going to fix any PHP7 issues - but we no longer have a goal of fixing all of them, or targeting any specific version of PHP. This issue seems to be asking for the latter.

[photodude]

I read it as HHVM is moving towards only supporting Hack. All of my reported issues were related to trying to run PHP code, as such I closed them. Feel free to reopen them if they are of interest. Unfortunately, all of my reported HHVM issues seemed dead in the water with no activity for over a year.