Convert an old mysql_ code into mysqli_ queries

Question

I am trying to convert an old mysql_ code into mysqli_ renaming all to mysqli_ doesn't work, I keep getting "Warning: mysqli_query() expects at least 2 parameters, 1 given in" and "Warning: mysqli_error() expects parameter 1 to be mysqli, string given in" could anyone help me on this on how can I convert the code below to work. I can't find an easy to understand tutorial.

function TicketFetcher(){
  $ticketsSQl = "SELECT tickets FROM tickets";
  $ticketsResult = mysqli_query($ticketsSQl) or die("Failed sql is " . 
  $ticketsSQl . "<br>Invalid query: " . mysqli_error());
  $tickets = mysqli_fetch_array($ticketsResult);
  $tickets = $tickets[0];

return $tickets;

}

Answer 1

Because in MySQLi functions we have to pass the connection information in functions
like this

mysqli_query($conn,$ticketsSQl);    
$conn =(host,username,password,dbname);