add multicall3

contracts/src/PBHEntryPointImplV1.sol

@@ -114,6 +114,9 @@ contract PBHEntryPointImplV1 is IPBHEntryPoint, WorldIDImpl {
     ///         World ID in a given month.
     uint8 public numPbhPerMonth;
 
+    /// @notice Address of the Multicall3 implementation.
+    address immutable multicall3;
+
     /// @dev Whether a nullifier hash has been used already. Used to guarantee an action is only performed once by a single person
     mapping(uint256 => bool) public nullifierHashes;
 
@@ -230,7 +233,9 @@ contract PBHEntryPointImplV1 is IPBHEntryPoint, WorldIDImpl {
     function pbhMulticall(
         IMulticall3.Call3[] calldata calls,
         PBHPayload calldata pbhPayload
-    ) external {}
+    ) external {
+        IMulticall3(multicall3).aggregate3(calls);
+    }
 
     // TODO: consider making this internal
     /// @param sender The sender of this particular transaction or UserOp.

contracts/src/interfaces/IMulticall3.sol

@@ -0,0 +1,97 @@
+// SPDX-License-Identifier: MIT
+pragma solidity >=0.8.12 <0.9.0;
+
+interface IMulticall3 {
+    struct Call {
+        address target;
+        bytes callData;
+    }
+
+    struct Call3 {
+        address target;
+        bool allowFailure;
+        bytes callData;
+    }
+
+    struct Call3Value {
+        address target;
+        bool allowFailure;
+        uint256 value;
+        bytes callData;
+    }
+
+    struct Result {
+        bool success;
+        bytes returnData;
+    }
+
+    function aggregate(
+        Call[] calldata calls
+    ) external payable returns (uint256 blockNumber, bytes[] memory returnData);
+
+    function aggregate3(
+        Call3[] calldata calls
+    ) external payable returns (Result[] memory returnData);
+
+    function aggregate3Value(
+        Call3Value[] calldata calls
+    ) external payable returns (Result[] memory returnData);
+
+    function blockAndAggregate(
+        Call[] calldata calls
+    )
+        external
+        payable
+        returns (
+            uint256 blockNumber,
+            bytes32 blockHash,
+            Result[] memory returnData
+        );
+
+    function getBasefee() external view returns (uint256 basefee);
+
+    function getBlockHash(
+        uint256 blockNumber
+    ) external view returns (bytes32 blockHash);
+
+    function getBlockNumber() external view returns (uint256 blockNumber);
+
+    function getChainId() external view returns (uint256 chainid);
+
+    function getCurrentBlockCoinbase() external view returns (address coinbase);
+
+    function getCurrentBlockDifficulty()
+        external
+        view
+        returns (uint256 difficulty);
+
+    function getCurrentBlockGasLimit() external view returns (uint256 gaslimit);
+
+    function getCurrentBlockTimestamp()
+        external
+        view
+        returns (uint256 timestamp);
+
+    function getEthBalance(
+        address addr
+    ) external view returns (uint256 balance);
+
+    function getLastBlockHash() external view returns (bytes32 blockHash);
+
+    function tryAggregate(
+        bool requireSuccess,
+        Call[] calldata calls
+    ) external payable returns (Result[] memory returnData);
+
+    function tryBlockAndAggregate(
+        bool requireSuccess,
+        Call[] calldata calls
+    )
+        external
+        payable
+        returns (
+            uint256 blockNumber,
+            bytes32 blockHash,
+            Result[] memory returnData
+        );
+}