[ThePhenix]

You can use:
https://sampwiki.blast.hk/wiki/SetPlayerWorldBounds

To limit a player to a certain area.

And you can also use:

PHP код:

IsPlayerInArea(playerid, Float:MinX, Float:MinY, Float:MaxX, Float:MaxY)
{
    new Float:X, Float:Y, Float:Z;
    GetPlayerPos(playerid, X, Y, Z);
    if(X >= MinX && X <= MaxX && Y >= MinY && Y <= MaxY) {
        return 1;
    }
    return 0;
} 


To check if the player is inside his land.