public function getEntity($tableName, $fieldList, $keyValueArray = NULL)
{
    // First construct the sql to be used to get the entity
    if(is_array($fieldList))
    {
        $sql = "SELECT ";
        foreach($fieldList as $field)
        {
            $sql .= $field." , ";
        }
        $sql = rtrim($sql, ' , ');
    }
    else
    {
        $sql = "SELECT ".$fieldList;
    }
    $sql .= " FROM ".$tableName;
    if($keyValueArray != NULL)
    {
        $sql .= " WHERE ";
        foreach($keyValueArray as $key => $value)
        {
            $sql .= $key." = ? AND ";
        }
        $sql = rtrim($sql, ' AND ');
    }
    //Then grab the connection
    $connection = $this->getConnection();
    //Prepare the statement
    $stmt = $connection->prepare($sql);
    if($stmt === false)
    {
        trigger_error('Wrong SQL: ' . $sql . ' Error: ' . $connection->errno . ' ' . $connection->error, E_USER_ERROR);
    }
    // Bind the paramaters
    if($keyValueArray != NULL AND count($keyValueArray) < 2)
    {
        $stmt->bind_param("s", $keyValueArray[key($keyValueArray)]);
    }
    elseif($keyValueArray != NULL)
    {
        $valueArray = array();
        $string = NULL;
        for($i = 0; $i < count($keyValueArray); $i++)
        {
          $string .= "s"; // for temp solution
        }
        $valueArray[] = &$string;
        foreach($keyValueArray as $key => $value)
        {
            $valueArray[] = &$keyValueArray[$key];
        }
        call_user_func(array($stmt, 'bind_param'), $valueArray);
    }
    //Execute the statement
    $stmt->execute();
    //Grab the results and stuff into multidimensional array
    $data = $stmt->result_metadata();
    $fields = array();
    $currentrow = array();
    $results = array();
        //Store references to keys in $currentrow
    while ($field = mysqli_fetch_field($data))
    {
      $fields[] = &$currentrow[$field->name];
    }
        // Bind statement to $currentrow using the array of references
    call_user_func_array(array($stmt, 'bind_result'), $fields);
        // Iteratively refresh $currentrow array using "fetch", store values from each row in $results array
    $i = 0;
    while ($stmt->fetch())
    {
        $results[$i] = array();
        foreach($currentrow as $key => $val)
        {
        $results[$i][$key] = $val;
        }
    $i++;
    }
    $connection->close();
    return $results;
}

$keyValueArray['firstName'] = 'John';
$keyValueArray['lastName'] = 'Doe';
$fieldListArray[] = 'firstName';
$fieldListArray[] = 'lastName';
print_r($db->getEntity('ACCOUNT', $fieldListArray, $keyValueArray));

Wrong parameter count for mysqli_stmt::bind_param()