You can use Laravel, a popular PHP web application framework, to build a Web3 smart contract by installing the necessary libraries and tools to interact with the Ethereum blockchain using PHP.

A sample code is provided that shows how to create a simple smart contract with "get" and "set" functions. You need to create a Laravel controller, update Laravel routes, and create views to interact with the smart contract. You also need to deploy the smart contract to the Ethereum network using Remix or Truffle and obtain the contract address and ABI.

Additional error handling, validation, and security measures may need to be added depending on the specific use case.