[Golf]

You can use this functions to change the material & the text of the object you created and attached to vehicle.
https://sampwiki.blast.hk/wiki/SetObjectMaterial
https://sampwiki.blast.hk/wiki/SetObjectMaterialText

This might not be correct, but you can get idea how to make it.

PHP код:

CMD:vehtext(playerid,params[])
{
new text;
if(sscanf(params,"s",text)) return SendClientMessage(playerid,0xCCCCCCAA,"/vehtext [text]");
new myobject = CreateObject(19353, 0, 0, 10, 0.0, 0.0, 90.0); //create the object
    SetObjectMaterialText(myobject,text, 0, OBJECT_MATERIAL_SIZE_256x128,\
    "Arial", 28, 0, 0xFFFF8200, 0xFF000000, OBJECT_MATERIAL_TEXT_ALIGN_CENTER);
return 1;
}