Call to a member function query() on null in PHP - php

Question

I am getting below error when I run my PHP code.
Call to a member function query() on null
Below is the code,
function fetch_url($url_code) {
$query = "SELECT * FROM `urls` WHERE `url_code` = ? ";
$result = $this->db->query($query, array($url_code));
if ($result) {
return $result;
} else {
return false;
}
}
Please guide me how to remove this error.

Answer 1

this->db->query function need only SQL Code. not like PDO.
Make sure Library is loaded
In config/autoload.php add this $autoload['libraries'] = array('database');
Try this
function fetch_url($url_code) {
$query = $this->db->query("SELECT * FROM urls WHERE url_code = '$url_code' ");
$result = $query->result_array(); # setting array to objective
$count = count($result); # get count
if (!empty($count)) {
return $result;
}
else {
return false;
}
}

Answer 2

Your $this->db is null. Please make sure, it is initialized properly before calling query. Here is a very basic example for MySQL (you will have to adapt it to your DB system):
function init() {
$this->db = new mysqli('host', 'user', 'password', 'database');
if (!$this->db) {
die('MySQL Connection Error (' . mysqli_connect_errno() . ') '
. mysqli_connect_error());
}
}
function fetch_url($url_code) {
$sql = "SELECT * FROM urls WHERE url_code = '$url_code' ";
if ($this->db === null) {
$this->init();
}
$query = $this->db->query($sql);
$result = $query->result_array(); # setting array to objective
$count = count($result); # get count
if (!empty($count)) {
return $result;
}
else {
return false;
}
}

Answer 3

class Database {
public $host=DB_HOST; // Specify localhost
public $username=DB_USER; //Specify username
public $password=DB_PASSWORD; // specify password
public $dbname=DB_NAME; // specify database name
public $conn ;
public $error;
/*
* Class Constructor
*/
Public function __constructor() {
// Call Connect Function
$this->connect();
}
/*
* Connector
*/
Public function connect() {
//* Creating mySqli Class Object * //
$this->conn = new mysqli($this->host,$this->username,$this->password,$this->dbname);
if (!$this->conn) {
$this->error = "Connection failed :" .$conn->connect_error ;
return false;
}
}
/*
* Select function
*/
public function select($query) {
/* to avoid call to member function query() on Null Error
Use this 2 lines of code */
if ($this->conn === null) {
$this->connect();
}
$results = $this->conn->query($query) or die($this->conn->error.__LINE__);
/* If there is atleast one row in the table Condition is true / Return table Rows as per your sql query */
if($results->num_rows > 0) {
return $results;
}
else {
return false;
}
} //Select Function Ends;
} //Class ends here ..

Answer 4

Yes use this lines of code to get rid of the error Call to a member function query() on null in PHP I used it in my database class and it's working fine !

Answer 5

class Database {
public $host='localhost'; // Your Local Computer
public $username='root'; // Your PhpMyAdmin Username
public $password=''; // Your PhpMyAdmin Password
public $dbname='blog'; // Your database Name
// Declaring Variables
public $conn ;
public $error;
/*
* Class Constructor
*/
Public function __constructor() {
// Call Connect Function
$this->connect();
}
/*
* Connector
*/
Public function connect() {
//* Creating mySqli Class Object * //
$this->conn = new mysqli($this->host,$this->username,$this->password,$this->dbname);
if (!$this->conn) {
$this->error = "Connection failed :" .$conn->connect_error ;
return false;
}
}
/*
* Select function
*/
public function select($query) {
// these 2 lines of code help to resolve error "Call to a member function query() on null " //
if ($this->conn === null) {
$this->connect();
}
$results = $this->conn->query($query) or die($mysqli->error.__LINE__);
/* If there is atleast one records in the table based on Sql Query ! Condition is true / Return table Records*/
if($results->num_rows > 0) {
return $results;
}
else {
return false;
}