forward Float:GetDistanceBetweenPlayers(p1,p2);
public Float:GetDistanceBetweenPlayers(p1,p2)
{
    new Float:x1,Float:y1,Float:z1,Float:x2,Float:y2,Float:z2;
    if(!IsPlayerConnected(p1) || !IsPlayerConnected(p2)) {
        return -1.00;
    }
    GetPlayerPos(p1,x1,y1,z1);
    GetPlayerPos(p2,x2,y2,z2);
    return floatsqroot(floatpower(floatabs(floatsub(x2,x1)),2)+floatpower(floatabs(floatsub(y2,y1)),2)+floatpower(floatabs(floatsub(z2,z1)),2));
}


stock GetClosestPlayer(p1)
{
    new x,Float:dis,Float:dis2,player;
    player = -1;
    dis = 99999.99;
    for (x=0;x<MAX_PLAYERS;x++) {
        if(IsPlayerConnected(x)) {
            if(x != p1) {
                dis2 = GetDistanceBetweenPlayers(x,p1);
                if(dis2 < dis && dis2 != -1.00) {
                    dis = dis2;
                    player = x;
                }
            }
        }
    }
    return player;
}

new victimid = GetClosestPlayer(playerid);
if(GetDistanceBetweenPlayers(victimid,playerid) < 4)
{
//ya code
}