how to send object/database connection to function in php - php

Question

i open a sql connection and try to send it to another function and it doesnt work .
its probbably something with sintax ,
i search all over the internet and couldnt find it .
my code :
$mainDataBase = mysqli_connect(/...../);
if ($mainDataBase->connect_errno) {
printf("Connect failed: %s\n", $mainDataBase->connect_error);
die;
}
/**
* 1 -> logIn && getInformation
*
* */
switch ($whichOperation){
case 1:
$gettingPlayerNumber = checkIfPlayerExist($mainDataBase, $playerName, $playerPass);
if($gettingPlayerNumber == 0){
echo "F";
die;
}
... keep going ...
function ::
function checkIfPlayerExist($dataBase ,$playerName ,$pass ){
$result = $dataBase->query("select playerNumber from PlayerInformation where (playerAccount = '" . $playerName ."') && (playerPass = " . $playerPass .")");
$row = $result->fetch_assoc();
if($row != null)
return $row['playerNumber'];
return 0;
}
its says:
Call to a member function fetch_assoc() on a non-object.
thank you for your time.
after some of the answer i checked and $result is null , but i checked the query before and now and it works!.
pass is int so it doesnt need any '' around it in the query.*
its connected succsesfully to the database - i checked this too

Answer 1

there seems to be a bug in your query,near password,missing quotes:
change,
$result = $dataBase->query("select playerNumber from PlayerInformation where (playerAccount = '" . $playerName ."') && (playerPass = " . $playerPass .")");
to
$result = $dataBase->query("select playerNumber from PlayerInformation where (playerAccount = '" . $playerName ."') && (playerPass = '" . $playerPass ."')");