[SilentSoul]

pawn Код:

ShowModelSelectionMenuEx(playerid, items_array[], item_amount, header_text[], extraid, Float:Xrot = 0.0, Float:Yrot = 0.0, Float:Zrot = 0.0, Float:mZoom = 1.0, dialogBGcolor = 0x4A5A6BBB, previewBGcolor = 0x88888899 , tdSelectionColor = 0xFFFF00AA)

forward OnPlayerModelSelectionEx(playerid, response, extraid, modelid);

Move your codes to OnPlayerModelSelectionEx instead of public OnPlayerModelSelection(playerid, response, listid, modelid)
https://sampforum.blast.hk/showthread.php?tid=407045
Take a look there also that example created by d0

pawn Код:

public OnPlayerCommandText(playerid, cmdtext[])
{
    if(strcmp(cmdtext, "/selectVehicleTrailer", true) == 0)
    {
        new cars[15];
        cars[0] = 435;
        cars[1] = 450;
        cars[2] = 569;
        cars[3] = 570;
        cars[4] = 584;
        cars[5] = 590;
        cars[6] = 591;
        cars[7] = 606;
        cars[8] = 607;
        cars[9] = 608;
        cars[10] = 610;
        cars[11] = 611;
        ShowModelSelectionMenuEx(playerid, cars, 12, "Select trailer", CUSTOM_TRAILER_MENU, 16.0, 0.0, -55.0);
        return 1;
    }
    return 0;
}

public OnPlayerModelSelectionEx(playerid, response, extraid, modelid)
{
    if(extraid == CUSTOM_TRAILER_MENU)
    {
        if(response)
        {
            SendClientMessage(playerid, 0xFF0000FF, "Trailer Spawned");
            new Float:pos[3]; GetPlayerPos(playerid, pos[0], pos[1], pos[2]);
            CreateVehicle(modelid, pos[0] + 2.5, pos[1], pos[2] + 2.5, 0.0, random(128), random(128), -1);
        }
        else SendClientMessage(playerid, 0xFF0000FF, "Canceled trailer selection");
    }
    return 1;
}