Correct inline documentation about `IMAGETYPE_WEBP` and `IMG_WEBP`

[GaryJ]

From ticket:35725#comment:195:

The // WebP constants are only defined in PHP 7.1+. comment in the code suggests that both IMAGETYPE_WEBP and IMG_WEBP were defined in PHP 7.1.

According to ​https://www.php.net/manual/en/function.imagetypes.php and ​https://www.php.net/manual/en/image.constants.php, the IMG_WEBP constant was available at 7.0.10, so the current comment is misleading.

This inline comment should be updated to be accurate.

[desrosj]

Changing the reporter to reflect who first noticed the issue.

[SergeyBiryukov]

Thanks for catching this! Looks like it should be two separate comments:

// IMAGETYPE_WEBP is only defined in PHP 7.1 or later.
if ( ! defined( 'IMAGETYPE_WEBP' ) ) {
	define( 'IMAGETYPE_WEBP', 18 );
}

// IMG_WEBP is only defined in PHP 7.0.10 or later.
if ( ! defined( 'IMG_WEBP' ) ) {
	define( 'IMG_WEBP', IMAGETYPE_WEBP ); // phpcs:ignore PHPCompatibility.Constants.NewConstants.imagetype_webpFound
}

[SergeyBiryukov]

In 51474:

Docs: Correct a comment about WebP constants in wp-includes/compat.php.

Follow-up to [50810], [50814].

Props GaryJ, rtm909.
Fixes #53680.

[SergeyBiryukov]

Reopening for 5.8.1 consideration.

[desrosj]

In 51508:

Docs: Correct a comment about WebP constants in wp-includes/compat.php.

Follow-up to [50810], [50814].

Props GaryJ, rtm909, SergeyBiryukov.
Merges [51474] to the 5.8 branch.
Fixes #53680.