> For the complete documentation index, see [llms.txt](https://docs.kojascripts.eu/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.kojascripts.eu/koja-lib/api-reference/client-api/callbacks.md).

# Callbacks

koja-lib provides a callback system that lets client scripts request data from the server and vice versa.

## TriggerServerCallback

Trigger a callback registered on the server and receive the result asynchronously.

```lua
KOJA.Client.TriggerServerCallback(key, payload, callback)
```

| Parameter  | Type       | Description                       |
| ---------- | ---------- | --------------------------------- |
| `key`      | `string`   | Callback identifier               |
| `payload`  | `any`      | Data sent to the server           |
| `callback` | `function` | Called with the server's response |

**Example**

```lua
KOJA.Client.TriggerServerCallback('myScript:getPlayerData', nil, function(data)
    print('Player name:', data.name)
    print('Money:', data.money)
end)
```

## RegisterClientCallback

Register a callback on the client that the server can trigger.

```lua
KOJA.Client.RegisterClientCallback(key, handler)
```

| Parameter | Type                    | Description                                     |
| --------- | ----------------------- | ----------------------------------------------- |
| `key`     | `string`                | Callback identifier                             |
| `handler` | `function(payload, cb)` | Handler function — call `cb(result)` to respond |

**Example**

```lua
KOJA.Client.RegisterClientCallback('myScript:getLocalPos', function(payload, cb)
    local coords = GetEntityCoords(PlayerPedId())
    cb({ x = coords.x, y = coords.y, z = coords.z })
end)
```

## Registering a Server Callback

On the server side you register the handler:

```lua
KOJA.Server.RegisterServerCallback('myScript:getPlayerData', function(source, payload, cb)
    local name = KOJA.Server.GetPlayerName(source)
    local money = KOJA.Server.getMoney(source, 'cash')
    cb({ name = name, money = money })
end)
```

See [Server Callbacks](file:///9510884/server/callbacks.md) for full server-side documentation.


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