To ensure the public/ directory is correctly exposed when deploying a PHP project on Vercel, you need to configure the routing so that all incoming requests are internally directed to that folder. This allows users to access the app without explicitly including public/ in the URL. Typically, this is done by setting up URL rewrites in the deployment configuration so that the public/ folder acts as the root for your application. Additionally, it’s important to place all your public-facing files inside that directory and avoid referencing the public/ folder in your paths or links directly. This setup helps maintain a clean and secure URL structure while aligning with Vercel's deployment model.