If you absolutely need to decode the file (for learning/fixing), run the encoded app on PHP 7.4 with IonCube loader, then use a (xdebug) or a compatible bytecode disassembler to inspect logic. Then rewrite the functionality for PHP 8.1 manually.

Searching for a "proper review" of an reveals that no official tool exists, as ionCube is a proprietary encryption and obfuscation system designed specifically to prevent decoding.

PHP 8.1 changed the way Opcodes (the instructions the server reads) are handled. Because ionCube works by replacing standard PHP execution with its own closed-source loader, "reversing" this process requires deep knowledge of the Zend Engine.

In desperation, John searched online for an IonCube decoder that could help him decode the encoded PHP files. He stumbled upon a website that claimed to offer a free IonCube decoder for PHP 8.1. John downloaded the decoder and installed it on his server.