警告:mysqli_query():无法获取mysqli

I have a problem where I can not retrieve the result from my MySQL database (via PHP). I use the same function in other places and it works flawlessly. However at this point i keep getting the "Warning: mysqli_query(): Couldn't fetch mysqli" error. Details of the problem are explained below. I use a quite similar function elsewhere (getAllCountries as seen below) in my PHP which does work perfectly:I have a problem where I can not retrieve the r