Lumen 9 PHP 8.0 Minimum Version Change Causes Fatal Errors in Legacy Facades

Developers need to confirm that custom facades and service providers continue to operate after upgrading a Lumen application from version 8.x to 9.x, given the framework’s new PHP 8.0 minimum requirement. The shift removes support for PHP 7.x‑specific constructs such as the each() function and certain mb_ereg_* calls without explicit encoding, meaning any facade or provider that still relies on these features will trigger a fatal error during bootstrap.

Because the migration guide only advises manual testing, it remains unclear which existing code bases or third‑party packages contain hidden calls to deprecated PHP 7.x functionality. What automated analysis can identify usage of removed PHP 7.x functions within facades before the upgrade? How should service providers be audited for compatibility with PHP 8.0’s stricter type system? Is there a supported shim or polyfill that allows legacy code to run safely on Lumen 9 without modifying the original source?