Update class name to RCE20 to avoid this type of conflict:
$ ./phpggc Laravel/RCE20 phpinfo 1
PHP Fatal error: Cannot declare class GadgetChain\Laravel\RCE19, because the name is already in use in phpggc/gadgetchains/Laravel/RCE/19/chain.php on line 5
Fatal error: Cannot declare class GadgetChain\Laravel\RCE19, because the name is already in use in phpggc/gadgetchains/Laravel/RCE/19/chain.php on line 5
Update class name to RCE20 to avoid this type of conflict: