PHP - 从MySQL Query获取字符串

I need to retrieve a string from a query and then use that later on in another SQL query.

This is what I have, I'm retrieving the current branch ID for the currently logged in user:

$neededBranch = mysqli_query($con, "SELECT BranchNumber FROM Staff WHERE staffID = '".$_SESSION['username_login']."'");

And then I need to use said string here like this:

$result = mysqli_query($con, "INSERT INTO SomeTable (
                    blah,
                    blah,
                    )
                    VALUES ('".$SomeValue."',"
                              . " '".$_SESSION['username_login']."',"
                              . " '".$neededBranch."')");

Now, the ". " '".$neededBranch."')");" does not work because it is expecting a string.

My question is: How do I actually get the value I'm needing from the first query and use it in the second query? I'm new at PHP and don't have a clue.

Fetch the data you queried:

$result= mysqli_query($con, $query);//query is the select stmt
$row = mysqli_fetch_assoc($result);
$neededBranch = $row['BranchNumber'];