PHP mysqli query: couldn't fetch mysqli - php

Question

I am trying to make a db connection and check a table for existing data. However I recieve this error and I am unable to find the cause:
Warning: mysqli::query(): Couldn't fetch mysqli in
/usr/share/nginx/www/me/container/class_lib.php on line
33 Warning: mysql_fetch_assoc() expects
parameter 1 to be resource, null given in
/usr/share/nginx/www/me/container/class_lib.php on line
97
class dbHandler {
static $dbObj = null;
protected $db_host = 'localhost'; #db host
protected $db_username = 'user'; #db username
protected $db_password = 'password'; #db password
protected $db_name = 'db'; #db name
function __construct()
{
# connect if not connected
if(self::$dbObj === null)
{
self::$dbObj = new mysqli($this->db_host, $this->db_username, $this->db_password, $this->db_name)
or die($this->dbObj->error);
}
mysqli_set_charset(self::$dbObj, "utf8");
}
// query: query the db
public function query($query)
{
return self::$dbObj->query($query);
}
}
/*
class userLogin
create user login
*/
class userLogin {
private $username;
private $password;
function __construct($username, $password) {
$this->_dbConn = new dbHandler();
$this->username = $username;
$this->password = $password;
}
public function verifyCredentials() {
if($this->verifyUsername())
{
} else {
exit;
}
if($this->verifyPassword())
{
} else {
exit;
}
}
private function verifyUsername() {
if(!(preg_match('/[^a-z_\-0-9]/i', $this->username)))
{
return true;
}
}
private function verifyPassword() {
$query = "SELECT * FROM tbl_user";
$result = $this->_dbConn->query($query);
$row = mysql_fetch_assoc($result);
var_dump($row);
}
}
What am I doing wrong here?

Answer 1

All your wrapper is over a mysqli object oriented way, and suddenly you have this line?
$row = mysql_fetch_assoc($result);
You have to use the fetch_assoc from the mysqli result object
$result->fetch_assoc()

Answer 2

Your SQL query is clearly failing. Why you have a function query to call a query I don't know but I have a feeling that is the route cause of your issue. You would be better off with something like this:
class dbHandler extends mysqli {
protected $db_host = 'localhost'; #db host
protected $db_username = 'user'; #db username
protected $db_password = 'password'; #db password
protected $db_name = 'db'; #db name
function __construct()
{
parent::__construct($this->db_host, $this->db_username, $this->db_password, $this->db_name);
if($this->connect_errno)
{
trigger_error('Unable to connect to the database [' . $this->connect_errno . ']: ' . $this->connect_error, E_USER_ERROR);
}
}
public function __destruct()
{
parent::close();
}
}
/*
class userLogin
create user login
*/
class userLogin {
private $username;
private $password;
function __construct($username, $password) {
$this->_dbConn = new dbHandler();
$this->username = $username;
$this->password = $password;
}
public function verifyCredentials() {
if($this->verifyUsername())
{
} else {
exit;
}
if($this->verifyPassword())
{
} else {
exit;
}
}
private function verifyUsername() {
if(!(preg_match('/[^a-z_\-0-9]/i', $this->username)))
{
return true;
}
}
private function verifyPassword() {
$query = "SELECT * FROM tbl_user";
$result = $this->_dbConn->query($query);
if($this->_dbConn->errno)
{
trigger_error('Error fetching users from table. Query: ' . $query . '. Error: ' . $this->_dbConn->error);
return false;
}
if($result->num_rows)
{
while($row = $result->fetch_assoc())
{
var_dump($row);
}
}
}
}
Let me know how you get on with that.

Answer 3

So... I never gave the mysql user from localhost any grants. Only from the remote LAN. Problemo solved.

Answer 4

Probably you are closing the connection too early? DBConnect->close();?
so, if you try to execute any query after that, you will get an error!