MySQLI Query issue

Hi Guys

Why is it that when i put this inside a function it does not work, but if I create my own MySQLI connection inside the function it does work

function name{
global $wpdb;
    $options = array();
	$res=mysqli_query($wpdb,"select ID,County from counties ORDER BY County ASC");
	$value="";
	$label="Please select a county";
	$options[] = array('label' => $label, 'value' => $value);
		while($row=mysqli_fetch_array($res)) {
		$sC=$row['ID'];
		$res1=mysqli_query($wpdb,"select County from wedding_shows where County='$sC'");
			if (mysqli_num_rows($res1) == 0) {
			} else {
			$options[] = array('label' => $row['County'], 'value' => $row['ID']);
			}
		}
}

Here are the errors i get

Warning: mysqli_query() expects parameter 1 to be mysqli, object given eval()’d code on line 3

Warning: mysqli_fetch_array() expects parameter 1 to be mysqli_result, null given eval()’d code on line 4

and here is it working with my own connection

function name(
$dbhost1 = 'localhost';
$dbuser1 = 'user';
$dbpass1 = 'pass';
$dbname1 = 'DBName';

$conn=mysqli_connect("localhost","$dbuser1","$dbpass1","$dbname1");
$options = array();
$res=mysqli_query($conn,"select ID,County from counties ORDER BY County ASC");
	$value="";
	$label="Please select a county";
	$options[] = array('label' => $label, 'value' => $value);
		while($row=mysqli_fetch_array($res)) {
		$sC=$row['ID'];
		$res1=mysqli_query($conn,"select County from wedding_shows where County='$sC'");
			if (mysqli_num_rows($res1) == 0) {
			} else {
			$options[] = array('label' => $row['County'], 'value' => $row['ID']);
			}
                 }
}