PHP mysqli bind_params error

Question

I'm having trouble getting this php script working with mysqli. I'm using Apache server, PHP 5.5, mysqli. The connection works, and I have other statements working properly (not with bind though).

// NOTE: servername, username, password defined but not shown

// Create connection
$conn = new mysqli($servername, $username, $password);

// Check connection
if ($conn->connect_error) {
    // database connection error
    echo '1';
    $conn->close();
    exit();
} 
$sqlQuery = "INSERT INTO 'fishingusers' SET 'deviceID' = ?, 'nickname' = ?,     'valid_on' = 'NOW()', 'valid_until' = 'null'";

echo ' '. $sqlQuery . '';

$deviceID = $conn->real_escape_string($_GET['deviceID']);
$nickname = $conn->real_escape_string($_GET['nickname']);

$stmt = $conn->prepare($sqlQuery);
$stmt->bind_param('ss', $deviceIDValue, $nicknameValue);

$deviceIDValue = $deviceID;
$nicknameValue = $nickname;

if($stmt->execute()) {
    // insert success
    echo '0';
}
else {
    // insert failed
    echo '3';
}

$conn->close();

I am receiving this error:

Fatal error: Call to a member function bind_param() on a non-object in XXXX on line 27

Line 27 is the $stmt->bind_param(). Sorry, I'm very new to PHP... this seems pretty simple.