wp-includes/Requests/src/Utility/CaseInsensitiveDictionary.php:61Get the value for the item
$offsetstringstring|null #[ReturnTypeWillChange] public function offsetGet($offset) { if (is_string($offset)) { $offset = strtolower($offset); } if (!isset($this->data[$offset])) { return null; } return $this->data[$offset]; }Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/Requests/src/Utility/CaseInsensitiveDictionary.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.