NewConstants: add missing IMAGETYPE_AVIF and IMAGETYPE_HEIF constants

[rodrigoprimo]

This PR adds two missing IMAGETYPE_* constants found while working on PHPCompatibility/PHPCompatibilityWP#88.

PHP 8.1 | NewConstants: add missing IMAGETYPE_AVIF constant

The IMAGETYPE_AVIF constant was introduced in PHP 8.1 as part of AVIF image support for getimagesize() and imagecreatefromstring().

Refs:

• https://www.php.net/manual/en/image.constants.php#constant.imagetype-avif
• php/php-src@cee33ba
• AVIF support for getimagesize() and imagecreatefromstring() php/php-src#7091

Related to #1299

PHP 8.5 | NewConstants: add IMAGETYPE_HEIF constant

The IMAGETYPE_HEIF constant was introduced in PHP 8.5 as part of HEIF/HEIC image support for getimagesize().

Refs:

• php/php-src@dfac2da
• Add support to get size of image from HEIF/HEIC php/php-src#18940

Related to #1849

[jrfnl]

Thanks for this PR @rodrigoprimo !

And well done not adding the gd extension (as, while the name is misleading, these constants are actually part of PHP standard (Core)).

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It looks like both constants are missing from the respective UPGRADING files in PHP itself.

While I imagine a PR to PHP 8.1 will no longer be accepted, I would like to suggest to you to submit a PR to the PHP 8.5 branch to update the UPGRADING file with a mention of this new constant.
Ref: https://github.com/php/php-src/blob/PHP-8.5/UPGRADING

I would also like to suggest creating a PR to update the PHP 8.1 and the PHP 8.5 migration guides as those are missing mentions of these constants too:

• https://www.php.net/manual/en/migration81.constants.php
• https://www.php.net/manual/en/migration85.constants.php

[jrfnl]

@rodrigoprimo Thanks for the update. Could you please squash those code style fixes into the correct original commits ?

[rodrigoprimo]

Thanks for the review, @jrfnl!

It looks like both constants are missing from the respective UPGRADING files in PHP itself.
I would also like to suggest creating a PR to update the PHP 8.1 and the PHP 8.5 migration guides as those are missing mentions of these constants too:

I went ahead and created the PRs you suggested:

php/php-src#20713
php/doc-en#5042
php/doc-en#5043