Below is the db connection class, but I am going to improve it by extending the PDO class itself:
<?php
class db{
private static $instance = NULL;
public function __construct() {
}
public static function getInstance() {
if (!self::$instance)
{
self::$instance = new PDO("mysql:host=localhost;dbname=dbmvc", 'root', '');;
self::$instance-> setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
return self::$instance;
}
private function __clone(){
}
}
?>
extended class:
<?php
class Model extends db{
final public function fetchInfo()
{
global $pdo, $db;
$query = $db->prepare("SELECT name FROM table");
$query->execute();
$result = $query -> fetchAll();
foreach( $result as $row )
{
echo $row['name'];
}
}
}
?>
But I have errors when I call this method:
$model=new Model();
$model->fetchInfo();
error is:
Call to a member function prepare() on a non-object in C:\xampp\htdocs\mvc\model\model.class.php on line 11
I am new to PDO, and I trying to figure it out but I can't find solution anywhere, can anyone help. Tnx!
This issue has nothing to do with PDO per se, but with object-oriented programming.
You declare global $db which you should be using self::$db or else making a distinct instance variable.
You didn't initialize $db before you called a method on it. You should set it to self::getInstance().
You declare a reference to a variable global $pdo which you never define and never use. This is just sloppy coding.
A model is not a database instance. You should prefer composition over inheritance in this case.
If you would like to see a very nice example of objects such as these I recommend reviewing this Database Class from the PHP-Login script by panique on GitHub. As well as this Model class from the same set of scripts. I hope this helps :D
Related
I'm new to using namespaces. In this example I made class, which handles database connection and I'm trying to use it inside the other classes. Can you explain what is wrong?
Connection.php
namespace Database;
class Connection
{
private static $instance = null;
private $pdo;
private function __construct()
{
$this->pdo = new PDO("mysql:host=localhost;dbname=database;", "root", "pw");
}
public static function get()
{
if (is_null(self::$instance))
self::$instance = new Connection();
return self::$instance;
}
}
Auth.php
namespace PHPAuth;
use Database\Connection;
class Auth
{
protected $dbh;
public function __construct()
{
$this->dbh = Connection::get();
...
Thanks in advance.
Edit: Ok, now I included autoloader and including class is now working correctly. But now I'm getting error when using $dbh in Auth like $query = $this->dbh->query("SELECT * FROM...");
Fatal error: Call to undefined method Database\Connection::query()
in...
First issue with class not found
I'll add the answer (which worked for you) for the first issue for reference: "Namespaces doesn't automatically load the files. You need to add an autoloader for that."
Second issue with undefined method
Fatal error: Call to undefined method Database\Connection::query()
The answer is in the error message. You've made the class Database\Connection into a singleton where Database\Connection::get() returns an instance of itself (which doesn't have any ->query() method), and not the actual PDO instance.
If you want that method to return the PDO instance instead, I would do something like this:
namespace Database;
use PDO;
class Connection
{
private static $pdo;
private function __construct()
{
// Leave the constructor private so it still becomes
// a singleton and so we can't instantiate this class.
}
public static function get()
{
if (is_null(self::$pdo)) {
self::$pdo = new PDO("mysql:host=localhost;dbname=database;", "root", "pw");
}
return self::$pdo;
}
}
Now the Connection class have become a Factory for the PDO-connection.
Connection::get() will return the same PDO instance over and over and you should be able to call $this->dbh->query("...") from your Auth class.
My question is rather simple and after checking a few bits and bobs on here I feel its best to ask a new question.
Lets say I have 2 classes
class FirstClass {
function test() {
return "info";
}
}
class SecondClass {
function test() {
return "info";
}
}
Then I have my mysqli object
$mysqli = new mysqli(host, user, password, db);
What do i need to do to be able to use the mysqli object inside the functions inside the classes.
This is my 2 thoughts so far although I haven't placed it on a site for testing yet.
class FirstClass {
global $mysqli;
function test() {
$mysqli->query("some query");
return "info";
}
}
or
class FirstClass {
function test() {
global $mysqli;
$mysqli->query("some query");
return "info";
}
}
I am pretty sure I can setup a construct if need be but I just need to know which way is the best way/only way to share the mysqli object.
Thanks
EDIT:
So I have done a hell of a load of learning and now have a lot more experience with passing info in and out.
Here is a latest working example type that I use.
namespace Page;
use mysqli;
class edit extends details{
protected $db;
//this function is actually in the details class but there is no point in demoing 2 classes
function __construct(mysqli $con){
$this->db = $con;
}
}
To expand what Kneel told you in comments and to counter the other answer
class foo {
function __construct($mysqli){
$this->mysqli = $mysqli;
}
function test() {
return $this->mysqli->query("some query");
}
}
is what it have to be.
You should create a mysqli instance somewhere outside the class and then pass it in coustructor.
You could use __construct() to initialize your MYSQLi. You can then access it around your class with $this.
class FirstClass {
public function __construct(){
$this->mysqli = new mysqli("host", "user", "password", "db");
}
function test() {
$this->mysqli->query("some query");
return "info";
}
}
If you wanted to use it in your second class too, you could construct it in the same way or extend your first class.
class SecondClass extends FirstClass {
public function __construct(){
parent::__construct();
}
function test() {
return "info";
}
}
I am building an API in PHP and I have a question. I'm using classes, and some of these classes need to access my database. However, I don't want to define variables for the database in every single class in order to open it, or have to send my mysqli object as a parameter of every single class constructor.
What would be the best way to go about this? Do I define a global variable of some kind?
A classic solution would be as follows
Create an instance of dbatabase handler class, either raw mysqli (worse) or better abstraction class (way better)
In the constructor of your application class take this db class instance as a parameter and assign it to a local variable
Use this variable with your class.
A quick example:
class Foo()
{
protected $db;
function __construct($db);
{
$this->db = $db;
}
function getBar($id)
{
return $this->db->getOne("SELECT * FROM bar WHERE id=?i", $id);
}
}
$db = new safeMysql();
$foo = new Foo($db);
$bar = $foo->getBar($_GET['id']);
How about using a static classes?
class mysqli_wrapper {
private static $db = null;
public static function open() {
GLOBAL $opts; // this can be global or setup in other ways
if (!self::$db) {
self::close();
self::$db = null;
}
self::$db = #mysqli_connect('p:'.$opts['hn'], $opts['un'], $opts['pw'], $opts['db']);
return self::$db;
}
public static function query($qry) {
return mysqli_query ( self::$db, $qry );
}
public static function affected_rows() { return #mysqli_affected_rows(self::$db); }
public static function error() { return #mysqli_error(self::$db); }
public static function close() { #mysqli_close(self::$db); }
} // end mysqli_wrapper
mysqli_wrapper::open(); // Here's how to call it
In a system I maintain my app needs to access its own MySQL db, as well as remote Oracle and SQL Server databases, and I use a trait for it. Here's a simplification of my code, just using MySQL:
dbaccess.php
trait DatabaseAccess {
protected $db;
private $host = 'host', $dbName = 'db', $username = 'username', $password = 'pword';
public function connectToMysql() {
$this->db= new mysqli(......);
}
}
then in myclass.php
require 'dbaccess.php';
class MyClass {
use DatabaseAccess;
//class code.....
}
All elements of DatabaseAccess will be available as if you hand-typed them in MyClass.
Note: if you're using PHP < 5.4, then this solution won't be possible.
I am switching my MVC to use PDO (I know, overdue). My application has, in the past, used the following class hierarchy:
Database.class>Main.class>User.class
(each one extending the other). But before any object is created, the mysql connection was made (mysql_connect). Once the connection was open I could use Database.class as a wrapper class through which all my queries were performed. Through extention, a query in the User.class could be made simply by calling the "query" function ($this->query).
Using PDO, I've tried to imitate the process but find errors. I created a singleton function in the Database.class:
function __construct()
{
$this->db = new PDO('mysql:host='.DB_HOST.';dbname='.DB_NAME.';charset=utf8', DB_USER, DB_PASSWORD);
$this->db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$this->db->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
}
public static function getInstance()
{
if (!isset(self::$instance)){
$object = __CLASS__;
self::$instance = new $object;
}
return self::$instance;
}
function query($qry,$params=NULL){
$qry = $this->db->prepare('SELECT * FROM users WHERE userID = :userID');
$qry->execute(array(':userID' => 1));
$results = $qry->fetchAll(PDO::FETCH_ASSOC);
return $results;
}
Then in Main.class I get the instance:
function __construct()
{
$this->db = parent::getInstance();
}
So in User.class I try to call
function __construct(){
parent::__construct();
}
function test(){
return $this->db->query("test");
}
So I can run any queries fine from the Main.class object. But if I try to run queries from User.class object I get the error: "Call to a member function query() on a non-object" In other words, if User.class extends main I should be able to access the variable $db in Main from User.class (I call the constructor for Main when the User object is created). Part of the issue is that Main.class is created earlier in the application as it's own object, I believe causing two instances of PDO to be created - which is why it doesn't work through extension (through a second object that also extends the database.class)
So my question is: is there a way to make this happen? Or is my best option to use injection for every object I create (because some scripts incorporate multiple objects that extend Main.class - which try to create an instance of PDO each time) and pass the pdo object to the constructor? I'd rather not have to do that (the less markup the better) So another option would be to use a STATIC variable that all classes use? What's the best method? (let me know if this is confusing)
I've seen people using injection for this, and I've seen examples of extending the pdo wrapper class (but only once).
Thanks! (I love stack overflow!)
You dont want any of these to extend the database class because that will essentially make them all singletons of which you can only have one instance... you Want to make them USE the database class instead. So you would put you most abstract db methods on the Database and then methods that create queries for specific things would be on the User or what have you. This means your Database actually wraps PDO and is what all other classes work with for db operations. The Main or Base class may not even be needed unless you are trying to implement active record or something.
class Database {
static protected $instance;
/**
* #var PDO
*/
protected $connection;
protected function __construct($dsn, $user, $pass, $attrs = array()) {
// create pdo instance and assign to $this->pdo
}
public static function getInstance() {
if(!self::$instance) {
// get the arguments to the constructor from configuration somewhere
self::$instance = new self($dsn, $user, $pass);
}
return self::$instance;
}
// proxy calls to non-existant methods on this class to PDO instance
public function __call($method, $args) {
$callable = array($this->pdo, $method);
if(is_callable($callable)) {
return call_user_func_array($callable, $args);
}
}
}
class Main {
protected $db;
public function __construct() {
$this->db = Database::getInstance();
}
}
class User extends Main{
public function __construct() {
parent::__construct();
}
public function findById($id) {
$qry = $this->db->prepare('SELECT * FROM users WHERE userID = :userID');
$qry->execute(array(':userID' => $id));
$results = $qry->fetchAll(PDO::FETCH_ASSOC);
return $results
}
}
I've trying to learn PHP OOP and have made some research on how to make a global database class to use around in my project. From what I've seen the most appropriate pattern available is a singleton which would ensure that only one database connection are present at all times. However as this is my first time working with the Singleton pattern, I am not sure that I have made it right.
Is this a proper singleton? Will this code ensure one database connection only? Is there any way I can test this? (Learn a man to fish and he will have food for the rest of his life...)
I am using redbean as my ORM and here's how I set it up plainly:
require_once PLUGINPATH.'rb.php';
$redbean= R::setup("mysql:host=192.168.1.1;dbname=myDatabase",'username','password');
I've made the following script based upon this source, as my own singleton Database class;
class database {
private $connection = null;
private function __construct(){
require_once PLUGINPATH.'rb.php';
$this->connection = R::setup("mysql:host=192.168.1.1;dbname=myDatabase",'username','password');
}
public static function get() {
static $db = null;
if ( $db === null )
$db = new database();
return $db;
}
public function connection() {
return $this->connection;
}
}
Thanks!
The instance variable needs to be a static member of the class. I haven't tested this code, but it should work. Connection should probably be static too. With this code, you will have one instance of your database class, and one instance of the connection. It is possible to do this without connection being static, but making it static will ensure there is only one connection instance. I also changed the literal names of the class to php magic constants. This make your code more maintainable. If you change the name of your class down the road, you won't have to go and find all of the literal instances of the old class name in your code. This may seem like overkill now, but trust me, as you work on more and more complex projects, you will appreciate the value.
class database {
private static $connection = null;
private static $db;
private function __construct(){
require_once PLUGINPATH.'rb.php';
self::$connection = R::setup("mysql:host=192.168.1.1;dbname=myDatabase",'username','password');
}
public static function get() {
if ( !(self::$db instanceof __CLASS__) ) {
$klass = __CLASS__; // have to set this to a var, cant use the constant with "new"
self::$db = new $klass();
}
return self::$db;
}
public function connection() {
return self::$connection;
}
}
You're singleton is almost correct.
The private member (no pun intended) $connection needs to be static as well. You might go with the following too:
class database {
private static $instance = NULL;
protected $conn;
private function __construct() {
$this->conn = mysql_connect( ... );
}
public static function init() {
if (NULL !== self::$instance)
throw new SingletonException();
self::$instance = new database();
}
public static function get_handle() {
if (NULL === self::$instance)
; // error handling here
return self::$instance->conn;
}
}