When you enter it sets your Pvp To on Says Welcome to You server name! and says please enjoy your stay here .
Code:
 #include "StdAfx.h"
#include "Setup.h"

#ifdef WIN32
#pragma warning(disable:4305)
#endif

void OnEnterWorld(Player * pPlayer)
{

    pPlayer->SendAreaTriggerMessage("Welcome to Your Server Name!");
    pPlayer->SetPvPFlag();;
    pPlayer->BroadcastMessage("Please Enjoy your stay here :D");

};
        
void SetupEnterWorld(ScriptMgr * mgr)
{
    mgr->register_hook(SERVER_HOOK_EVENT_ON_ENTER_WORLD, OnEnterWorld);
}