wp-includes/class-wp-image-editor.php:178Flips current image.
$horzbool$vertbooltrue|WP_Error abstract public function flip( $horz, $vert );Introduced in 3.5.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-image-editor.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.