Developers using Laravel Herd on macOS Monterey 12.x, particularly on Intel-based Macs, encounter a critical 'dyld: Symbol not found' error when updating to PHP 8.4. This runtime failure occurs because Laravel Herd's newer PHP binaries are compiled against a more recent C++ standard library (libc++) than what is available in macOS Monterey. The operating system's /usr/lib/libc++.1.dylib lacks the required symbols, causing immediate crashes for the php84 binary and preventing any Laravel artisan commands or PHP scripts from executing.

The issue stems from a binary compatibility mismatch rather than a framework bug. To resolve this, users must manually replace the incompatible binaries with older, compatible versions provided by Herd. Specifically, downloading PHP 8.4.15 x86 and FPM binaries and moving them to ~/Library/Application Support/Herd/bin/ is required.

After moving the files, applying correct permissions using 'chmod 755' is essential to ensure they execute properly. This manual downgrade restores functionality, allowing the CLI to report the correct version and enabling Laravel services to start without error. Similar compatibility fixes apply to older PHP 8.2 and 8.3 versions.