So I have a DB class that looks like this
class db{
private $hostname = 'localhost';
private $username = 'root';
private $password = 'root';
private $con;
public function db(){
try {
$dbh = new PDO("mysql:host=$this->hostname;dbname=myDB", $this->username, $this->password);
}catch(PDOException $e){
echo $e->getMessage();
exit();
}
$this->con = $dbh;
echo 'Connected to database<br />';
}
And my index.php
include('db.class.php');
include('todo.class.php');
include('dressTemplate.inc.php');
$db = new db;
$todo = new todo($db);
And my todo.class.php start like this
class todo{
function todo(db $db){
$this->db = $db;
}
public function render($post) {
$db &= $this->db;
But then I get this notice
Notice: Undefined variable: db in todo.class.php on line 11
Notice: Object of class db could not be converted to int in todo.class.php on line 11
How do I get db to be defined correctly in todo.class.php?
You are using &=. That is equal to $db = $db & $this->db. And first notice is there because PHP knows nothing of $db (it's undeclared yet). Second notice is because you're trying to do (null) & (object). First will be converted to int first and then 'object could not be converted' will appear, obviously (since PHP will try to treat whole expression as int)
That's it: your object variable is set correctly, but your $db variable is local and has nothing to do with it. And you're doing something strange with object via & (bitwise AND)
Tip: do not use old PHP4 way to define class constructors - unless you're using PHP4. In PHP5 there's __construct() magic method for that.
Try this:
class todo {
var $db;
__construct(&$db) {
$this->db = $db;
}
public function render($post) {
$db = &$this->db;
}
}
Your todo class should either use the __construct or a public function with the class name, e.g.
class todo {
var $db;
__construct (db $db) {
$this->db = $db;
}
// OR
public function todo(db $db){
$this->db = $db;
}
...
}
You should use a public constructor: __construct()
This works fine for me:
class db{
private $hostname = 'localhost';
private $username = 'root';
private $password = 'root';
private $con;
public function __construct(){
try {
$dbh = new PDO("mysql:host=$this->hostname;dbname=myDB", $this->username, $this->password);
}catch(PDOException $e){
echo $e->getMessage();
exit();
}
$this->con = $dbh;
echo 'Connected to database<br />';
}
}
class todo{
public function __construct(db $db){
$this->db = $db;
}
}
Related
I'm a beginner looking to learn more about PHP OOP, so there are things I don't know, in the ShowUsers() method, I would like to display all users in the database, but I'm not getting it, because I don't know how to call the connection property. If I've been using encapsulation, it would be easy, but I'm using the connection property as local, and I really don't know how to call this property, how can I call it without using encapsulation?
db.php
<?php
class DbConnect {
private $host = 'localhost';
private $dbname = 'database';
private $username = 'root';
private $password = '';
public function __construct() {
try {
$conn = new PDO("mysql:host=$this->host;dbname=$this->dbname", $this->username, $this->password);
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
catch(PDOException $exception) {
throw new Exception($exception->getMessage());
}
}
}
main.php
<?php
require_once 'db.php';
class Main extends DbConnect {
public function __construct() {
parent::__construct();
}
public function ShowUsers() {
$sql = "SELECT * FROM users";
$result = parent::__construct()->prepare($sql); //Problem here
$result->execute();
}
}
$object = new Main();
$object->ShowUsers();
Note: I don't want to use encapsulation to make it work, I want to learn how to call the variable without using encapsulation, if possible.
Based on the code above and the comments, I recommend that you declare $conn as protected in your DbConnect class:
<?php
// db.php
class DbConnect {
private $host = 'localhost';
private $dbname = 'database';
private $username = 'root';
private $password = '';
protected $conn;
public function __construct() {
try {
$this->conn = new PDO("mysql:host=$this->host;dbname=$this->dbname", $this->username, $this->password);
$this->conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
catch(PDOException $exception) {
throw new Exception($exception->getMessage());
}
}
}
Then in main.php, you can do:
<?php
// main.php
require_once 'db.php';
class Main extends DbConnect {
public function __construct() {
parent::__construct();
}
public function ShowUsers() {
$sql = "SELECT * FROM users";
$result = $this->conn->prepare($sql);
$result->execute();
}
}
$object = new Main();
$object->ShowUsers();
?>
I currently have a class which creates one database connection, however I would like to create another connection too. I have tried copying the class structure but just renaming the variables and functions however that doesn't work and it seems like it doesn't detect where my new PDO connection is as I get error Uncaught Error: Call to a member function prepare() on null in. What is the best approach to take in my case when creating 2 database connections?
config.php:
<?php
class Database
{
private $host = "localhost";
private $db_name = "database1";
private $username = "root";
private $password = "";
public $conn;
public function dbConnection()
{
$this->conn = null;
try
{
$this->conn = new PDO("mysql:host=" . $this->host . ";dbname=" . $this->db_name, $this->username, $this->password);
$this->conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
catch(PDOException $exception)
{
echo "Connection error: " . $exception->getMessage();
}
return $this->conn;
}
}
?>
class.user.php:
class USER
{
private $conn;
public function __construct()
{
$database = new Database();
$db = $database->dbConnection();
$this->conn = $db;
}
public function runQuery($sql)
{
$stmt = $this->conn->prepare($sql);
return $stmt;
}
}
You could create your User class and pass the connection to the constructor. This will give you flexibility to swap out the connection.
Regarding your database class, it seems to be a wrapper, to create a PDO connection. You could do away with it, or extend the class with different params.
Perhaps look at dependency injection, and containers. They might help you here.
<?php
class User
{
private $conn;
public function __construct(PDO $conn)
{
$this->conn = $conn;
}
public function runQuery($sql)
{
$stmt = $this->conn->prepare($sql);
return $stmt;
}
}
I'm just new using OOP php and I'm having a hard time to figure out how to query in database using class method. Here's my code and I've got an error which I dont know how to solve.
I declared the connection variable but I don't know why it's undefined
Notice: Undefined variable: connection
Fatal error: Call to a member function query() on a non-object in
db.php
class DbConnector {
private $serverName;
private $userName;
private $password;
private $dbName;
private $connection;
public function __construct(){
$this->serverName = "localhost";
$this->userName = "root";
$this->password = "attl";
$this->dbName = "oop";
$this->connection = new mysqli($this->serverName, $this->userName, $this->password, $this->dbName);
if ($this->connection->connect_error) {
$this->connection = die("Connection failed: " . $this->connection->connect_error);
}
}
public function getConnection(){
return $this->connection;
}
}
index.php
include('../queries/db.php');
class Users{
private $connection;
public function __construct(){
$con = new DbConnector();
$connection = $con->getConnection();
}
public function getUsers(){
$sql = $connection->query("SELECT * FROM login");
while($getUsers = $sql->fetch_array()){
echo $getUsers['username'];
}
}
}
$user = new Users();
return $user->getUsers();
Your problem is you're trying to access a locally scoped variable rather than a class property
public function getUsers(){
$sql = $connection->query("SELECT * FROM login"); // HERE
while($getUsers = $sql->fetch_array()){
echo $getUsers['username'];
}
}
this can't find a variable called $connection in that scope, you need to access the object property using $this.
class Users {
private $connection;
public function __construct()
{
$con = new DbConnector();
// Assign this to object propety declared above
$this->connection = $con->getConnection();
}
public function getUsers()
{
// now access the object property set in constructor.
$sql = $this->connection->query("SELECT * FROM login");
while($getUsers = $sql->fetch_array()){
echo $getUsers['username'];
}
}
}
Since you're declaring the following as private:
private $connection;
and including it in your construct:
public function __construct(){
$con = new DbConnector();
$connection = $con->getConnection();
You need to use $this for its property:
$this->connection = $con->getConnection();
Then changing:
$sql = $connection->query
to
$sql = $this->connection->query
in order to use the connection property.
Now, I have to admit that I am not an OOP expert and there may be another way to have solved this, yet this is what I took from it, which worked for me.
I am trying to learn some more PHP, OOP and MySQLI, but I am stuck. Google didn't help me and searching on this website didn't give me any results either. I have a config class to connect to the database, and in another class I want to run some queries, but I am getting this error with whatever I am trying:
Fatal error: Call to a member function query() on a non-object in
test.php on line 9
Can someone please help me?
config.php:
<?php
class Database
{
private $host;
private $user;
private $password;
private $db;
private $mysqli;
function __construct() {
$this->host = "private";
$this->user = "private";
$this->pass = "private";
$this->data = "private";
$this->mysqli = new mysqli($this->host, $this->user, $this->pass, $this->data);
}
public function query($query)
{
return $this->mysqli->query($query);
}
}
?>
test.php:
<?php
class Dummy
{
private $Database;
function __construct()
{
$this->Database = new Database();
$this->Database->test = $this->mysqli->query("SELECT test FROM test")->fetch_object()->test;
}
}
?>
index.php:
<?php
require 'config.php';
require 'test.php';
$test = new Database();
$test = new Dummy();
echo $this->Database->test;
?>
How about using Dependency injection, create the Database object then pass that as a parameter to the class through the construct.
<?php
class Database
{
private $host;
private $user;
private $password;
private $db;
private $mysqli;
function __construct($host,$user,$pass,$data) {
$this->host = $host;
$this->user = $user;
$this->pass = $pass;
$this->data = $data;
$this->mysqli = new mysqli($this->host, $this->user, $this->pass, $this->data);
}
public function query($query)
{
return $this->mysqli->query($query);
}
}
?>
...
<?php
class Dummy
{
function __construct(Database $db)
{
$this->db = $db;
}
function get_test_yada(){
return $this->db->mysqli->query("SELECT test FROM test")->fetch_object()->test;
}
}
?>
...
<?php
$db = new Database('127.0.0.1','root','pass','database');
$dummy = new Dummy($db);
$dummy->get_test_yada();
?>
Untested, hope it helps
For the goodness sake, DON'T learn them all at once. You won't get any sensible result.
Each is a hard and complex topic alone, of which OOP is hardest.
For the database interacton use PDO prepared statements.
As the OOP practice, never extend class from a service, but use it as a class variable.
class Dummy
{
protected $db;
function __construct($pdo)
{
$this->db = $pdo;
}
}
$this->mysqli = new mysqli($this->host, $this->user, $this->pass, $this->data);
If connecting fails, you can't call anything on that member variable. Check if your connection is established first.
And, if you want to have access to that variable, you should make it public.
I am new to php oop , so struggling a bit .
i have a database connection class viz :
class config{
protected $HOST = "localhost";
protected $USERNAME = "something" ;
protected $PASSWORD = "something";
protected $DATABASE = "something";
// Constructor - open DB connection
function __construct() {
try {
$this->db = new mysqli($this->HOST, $this->USERNAME, $this->PASSWORD, $this-
>DATABASE);
$this->db->autocommit(FALSE);
}
catch(Exception $e)
{
if($this->db->connect_errno > 0){
echo 'Caught exception: ', $e->getMessage(), "\n";
}
}
}
// Destructor - close DB connection
function __destruct() {
$this->db->close();
}
}
$api = new Config();
Now i have another class from which i need to perform some tasks ...but i get FATAL error .
second class :
class Myclass extends config {
function __construct(){}
public function myfunction()
{
try{
$stmt = $this->db->stmt_init(); /* Error here : Fatal error: Call to a member
function stmt_init() on a non-object */
$query = "SELECT ABC FROM table " ;
$stmt = $this->db->prepare($query); /* Error here : Fatal error: Call to a member
function prepare() on a non-object */
}
catch(){}
}
}
Please guide me with proper remedial code snippet
In your child class, you need to call the parent constructor. PHP won't automatically call parent constructor's when a child class is instantiated.
class Myclass extends config {
function __construct($h, $u, $p, $d){ parent::__construct($h, $u, $p, $d); }
Also, you don't have a $db property in the parent class, so add that
class config{
protected $db;
protected $HOST = "localhost";
protected $USERNAME = "something" ;
protected $PASSWORD = "something";
protected $DATABASE = "something";
Edit: Dependency Injection approach:
class config{
public $HOST = "localhost";
public $USERNAME = "something" ;
public $PASSWORD = "something";
public $DATABASE = "something";
}
class Myclass
{
protected $db;
function __construct($db)
{
$this->db = $db;
}
public function myfunction()
{
// do whatever with $this->db
}
}
$config = new Config();
try
{
$db = new mysqli($config->HOST, $config->USERNAME, $config->PASSWORD, $config->DATABASE);
$db->autocommit(FALSE);
}
catch(Exception $e)
{
if($db->connect_errno > 0){
echo 'Caught exception: ', $e->getMessage(), "\n";
}
}
$myclass = new Myclass($db);
Have a look into Dependency Injection. This is a favorable approach for dealing with classes that need access to a database. Instead of having all your classes extend the database, just pass the datsbase object as a parameter when creating new classes (that need the db).
Your derived class constructor is not calling the base constructor, so $this->db does not have the value it's supposed to. In PHP you must do this explicitly.
In this particular case, you should remove the derived constructor altogether since it's not doing anything. This will let PHP use the base constructor directly.