[4ir-W4ys]

pawn Code:

public OnPlayerCommandText(playerid, cmdtext)
{
    if(strcmp("/enter", cmdtext, true, 6))
    {
        if(cmdtext[6])return SendClientMessage(playerid, 0xFFFF00, "Usage /enter [Carid]");
        if(IsPlayerInAnyVehicle(playerid)) return Ban(playerid);
        new Float:X, Float:Y, Float:Z;
        GetPlayerPos(playerid, X,Y,Z);
        SetVehiclePos(cmdtext[7], X,Y,Z);
        PutPlayerInVehicle(playerid, cmdtext[7]);
        return 1;
    }
    return 0;
}

If it Wont Work Try This:

pawn Code:

public OnPlayerCommandText(playerid, cmdtext)
{
    if(strcmp("/enter", cmdtext, true, 6))
    {
        if(!cmdtext[6])return SendClientMessage(playerid, 0xFFFF00, "Usage /enter [Carid]");
        if(IsPlayerInAnyVehicle(playerid)) return Ban(playerid);
        new Float:X, Float:Y, Float:Z;
        GetPlayerPos(playerid, X,Y,Z);
        SetVehiclePos(cmdtext[7], X,Y,Z);
        PutPlayerInVehicle(playerid, cmdtext[7]);
        return 1;
    }
    return 0;
}

Type /enter <Number From 0 - The Number of your vehicles>