Today i tried to convert my functions to PHP Class.
I tried with some basic steps.
<?php
class DataBase {
private $host;
private $user;
private $password;
private $db;
private $mysqli;
function __construct() {
$this->host = "localhost";
$this->user = "root";
$this->password = "";
$this->db = "my_database";
$this->mysqli = new mysqli($this->host, $this->user, $this->password, $this->db);
}
function __destruct() {
$this->mysqli->close();
}
public function query($query, $params = '', $bind_result) {
$stmt = $this->mysqli->prepare($query);
//Need to change this to process the array of params
$stmt->bind_param('i', $params);
$stmt->execute();
//Change this to handle array of bind
$stmt->bind_result($bind_result);
//Loop the result and store it in a temp array
$stmt->fetch();
//Don't print the statement. Just close the statement and return the array.
printf("%s\n", $bind_result);
/* close statement */
$stmt->close();
}
}
?>
I have to now create another class. I created one dummy table in database.
<?php
class Dummy {
private $database;
function __construct() {
$this->database = new Database();
}
public function getAllDummy() {
$query = "SELECT name FROM dummy WHERE id = ?";
$this->database->query($query, 1, 'name');
}
}
?>
But I don't think it is the right way to do the things. I feel some of them are in the right way and some of them are wrong.
When i call the query() function, Do i need to connect the database all the time in every classes' construct method? Or Do i need to change the Database class to static functions? So i can call the functions like Database::query();
It seems i need to create everything from the start. Is such a model already available in internet? like cakephp, codeigniter
I would like to recommend you to read something about ORM for PHP. For example I m using Doctrine 2 (http://www.doctrine-project.org/) It is kinda complex but definitely worth to learn. There is everything you are trying to code already done, so why you should make it again?
In your OOP principe there are some mistakes.
You are creating Database instance for every class like Dummy, if you will have class Users, Articles, you will create 3x Database, it isnt really good. You should make Database as service or Singleton and make it just once. Good solution for this can be Dependency injection (http://en.wikipedia.org/wiki/Dependency_injection).
Also I would recommend you to generalize whole Dummy class, to make it more general. Dont make method "getAllDummy" but for example "getAll($tableName)"so you can use it for every table.
Besides Doctrine (Which is powerfull and almighty already but still to complex) I can suggest you db.php (http://dbphp.net) which does everything what doctrine but is single file and is very easy to use. Cons: It is not well documented yet and has no big community yet.
Related
I have a function like this:
function write_to_db($foo) {
$db = new PDO("sqlite:bar.db");
$query = $db->prepare("INSERT INTO table VALUES (?)");
$query->bind_param("s", $foo);
$query->execute();
}
Problem is that I am calling this function multiple times inside my php-script(s). Is there a way to make the $db variable static somehow so that it won't need to open & close the file multiple times during executing of the php-script?
Sending the database as a parameter is not an option as the function is called withing classes and other functions and then I would need to make all of them aware of the database.
Edit: ok, I was told this is the best practice and I guess I don't need to worry about performance.
Yes there is way to make it. You can do it via Singleton object. You can find more information about of Singleton Pattern.
So I made a simple implementation of it which what you want to do.
class SqliteSingleton
{
private static $connection = null;
public static function getConnection($path = null){
if ($this->connection == null) {
$this->connection = new PDO("sqlite:" . $path);
}
return $this->connection;
}
}
You can use it at anywhere you want.
$connection = SqliteSingleton::getConnection('bar.db');
Also you can do research and made more efficient class design then this.
I'm moving onto teaching myself OOP in PHP.
I'm creating a couple of little web apps and have followed a lot of tutorials that either create the database (using PDO) via a Singleton, or via passing the global around. I've read that these are pretty much the same thing and are both to be avoided like the plague.
So I've watched the Google Tech Talks on clean code, and read almost every SO article on dependency injection and the like. I have a couple of questions.
The clean code videos suggest you shouldn't do 'work' in your constructors. Is this 'work' in reference to business logic. Ie. If my class's job is to create another object, is that an OK kind of 'work'?
For example, in trying to conform to single repsonibility classes I created three.
Class DB - which actually connects to the database.
Class DBFactory - which creates the DB object which connects to the database.
Class DBInstance - which returns a single instance of the DBFactory created PDO object.
Please note that I'm trying to create a single instance, without creating a Singleton pattern.
So I try and pass my dependencies for each class up the chain. I find myself in a position where I have to create all of the objects (from DB down) so I can inject the dependencies. For some reason I thought it would work the other way, I'd create the first object, which would create the second for me etc. I'm clearly missing something?
Hopefully this helps others as well - there seems to be a myriad of questions relating to this stuff and databases but very little good examples.
(I should mention this does work, I do get a list of hotel names out of the database!)
TestCode.php
include './classes/DB.php';
include './classes/DBFactory.php';
include './classes/DBInstance.php';
include './classes/Location.php';
$db = new DB;
$dbfactory = new DBFactory($db);
$dbinstance = new DBInstance($dbfactory);
$dbh = $dbinstance->getDbInstance();
//Example business logic
$location_names = Location::getLocationNames($dbh);
print_r($location_names);
Class DB.php:
class DB {
private $_dbhost = 'myhost';
private $_dbname = 'myname';
private $_dbuser = 'myuser';
private $_dbpass = 'mypass';
private $_error;
public function connect() {
try {
return new PDO("mysql:host=$this->_dbhost;dbname=$this->_dbname",
$this->_dbuser, $this->_dbpass);
}
catch (PDOException $e) {
$this->_error = 'Error! ' . $e->getMessage() . '<br />';
die();
}
}
public function getError() {
if (isset($this->_error)) {
return $this->_error;
}
}
}
Class DBFactory.php
class DBFactory {
private $_dbh;
public function __construct(DB $db) {
$this->_dbh = $db;
}
public function Create() {
return $this->_dbh->Connect();
}
}
Class DBInstance.php
class DBInstance {
private static $_dbinstance;
public function __construct(DBFactory $dbfactory) {
if (!isset(self::$_dbinstance)) {
self::$_dbinstance = $dbfactory->Create();
}
}
public function getDbInstance() {
return self::$_dbinstance;
}
}
Your code seems to do what you want it to.. but maybe we can use less object instantiation using inheritance and maybe we can avoid static properties in instanciated classes.
Also in regard to using a pattern of dependency injection that is able to handle multiple connections, but support using a single instance of it. exemple first, classes after
$params = array
('host'=>'localhost',
'db'=>'ice',
'user'=>'kopitar',
'pass'=>'topnet',
'charset'=>'utf8'); // passing the charset explicitely is great
$handle = new handle($params);
$db = $handle->getInstance();
we can either pass the $db to our functions
$location_names = Location::getLocationNames($db);
or the whole $handle. as long as $handle is not reconstructed, it will always return the same database connection.
$location_names = Location::getLocationNames($handle);
if I want to reconstruct I need the whole $handle
$handle->__construct(/* params but with another database infos */);
$db2 = $handle->getInstance();
As for the classes, I think we want the params to arrive from the instanciated class, so we can change them later.
class db {
function __construct($params) {
foreach ($params as $param => $value) {
$this->{$param} = $value; // assigns the connections infos
}
}
protected function connect() {
$dsn = 'mysql:host='.$this->host.';dbname='.$this->db.';charset='.$this->charset;
return new PDO($dsn,$this->user,$this->pass);
}
}
the factory creates a connection from params and passes it to something else, good factory
class factory extends db {
protected function create() {
return $this->connect();
}
}
now we want to have our object to keep it's connection as long as we do not rebuild it. so we give it to instance
class instance extends factory {
function instantiate() {
$this->instance = $this->create();
}
}
and last but not least, our handle which returns the instance. it could be in instance class.....................
but I feel like having four and find no real reason not to.
class handle extends instance {
function __construct($params) {
db::__construct($params);
$this->instantiate(); // when we construct a handle, we assign an instance to the instance property
}
function getInstance() {
return $this->instance;
}
}
KISS
Don't make things more complex than they are, of course this is just my opinion, but as I see it you are building a complex solution for a problem that someone else says might exist is some cases.
Php is not multi threaded so there goes one of the biggest arguments overboard. (in very rare-occasions it might be)
I'm using singletons for my database connections for about 15 years now and never ever had a problem with them, I do play around with different connections having one singleton handle several connection instances, but whatever... it works great and everyone that looks at the code.. understands it directly.
I'm not using globals because they can be overwritten and are kind of hard to predict (when it holds the correct object, and when/why they don't)
Use OOP to make your code cleaner, easier to work with and more flexible.
Don't use it to fix problems that aren't there and make your code more complex because others tell you to.
An very simple example of a db-connection singleton class handling several different connections.
class singleton{
private static $_instances=array();
public static function getInstance($connectionName){
if(!isset(self::$_instance[$connectionName]){
self::$_instance[$connectionName]=self::_getConnection($connectionName);
}
return self::$_instance[$connectionName];
}
}
just my 2 cents
Why do you have a factory if you have a singleton? This is needless.
This is a never-ending debate, but I'm advocate of do not use singletons for database connections.
As far as in most applications, you have only one data channel, you can consider your database connection unique, but this might not be always true.
In deed, the effort made to create a singleton database connection is even bigger than just create a regular one.
Also, your class DB is not configurable, therefore, you need to change it when your connection parameters change. And I think DB is a very bad name for this.
I'd rather call this Storage and do something like:
inteface Storage {
public function insert($container, array $data);
public function update($container, array $data, $where);
public function delete($container, $where);
public function getAll($container);
public function getOne($identifier);
}
final class PdoStorage implements Storage {
private $dbh;
private $dsn;
private $user;
private $pswd;
public function __construct($dsn, $user, $pswd) {
$this->dsn = $dsn;
$this->user = $user;
$this->pswd = $pswd;
}
// Lazy Initialization
private function connect() {
if ($this->dbh === null)
$this->dbh = new PDO($this->dsn, $this->user, $this->pswd);
}
public function insert($container, array $data) {
$this->connect();
// ... omitted for brevity
}
}
Now, when you need a database storage, you do:
$someObj = new SomeClass(new PdoStorage(...));
Now you might be wondering if you will need to create an PdoStorage for each single object that depends on it.
The answer is: no!
Now you can use a factory to simplify your life.
class SomeFactory {
private $defaultStorage;
public function __construct(Storage $storage) {
$this->defaultStorage = $storage;
}
public function create($type) {
// Somehow fetches the correct class to instantiate and put it into $class variable , for example... and then
return new $class($this->defaultStorage); // Or you'd better do this with reflection
}
}
$factory = new SomeFactory(new PdoStorage(...));
$factory->create('SomeClass');
This way, you can have just one database connector or more if you need.
I've been taking help from this site by years now, but I have never asked, so this is my first question here. This is a theoretic question, I would like to know if I'm thinking in the right way.
First of all, sorry for my English.
I was thinking if I could simplify my existing MySQL object.
For the connection, I use the singleton pattern to ensure that my app connect only one time during script execution. So, in every class, when I want to use MySQL, a get the instance.
$db = db::getInstance();
$result = $db->query("SELECT * FROM data;");
the $result is a dbResult class, on which I can use loops (while($row = $result->nextRow()) {...}), jump to row number, etc...
after all things are done, then I $result->free(); the result class.
Question 1.
Why not return an associative array instead of the dbResult class? I could use a foreach on it. But what about a result with 1.000.000 rows?
Question 2.
Do I have to get the instance every time I want to use SQL?
class db{
...
private static $instance;
...
public static function query($_query){
if (!self::$instance){
self::$instance = new db(); //first we need to connect...
self::query($_query);
}
else{
//execute query, then load result in array,
//or in case of insert, return insert_id
return $return_array;
}
}
In this case, I can simply call a query from anywhere in my code without instantiating the db object.
$result = db::query("SELECT * FROM data;");
...
//or insert
db::query("INSERT INTO test VALUES ('test_value');");
Would be this a bad practice?
Have a look at Doctrine 2 for example. It's a big project, but when u master it, its damn awesome :)
If this is too big for you, refactor your class to not use singleton pattern implementation and/or static methods.
Here's what I suggest:
Create a Database class.
<?php
class Database {
private $db;
private $host;
private $username;
private $password;
// Should probably not put your DB credentials here, just the Databases, but its just here for this purpose
const DB_HOST = '';
const DB_USERNAME = '';
const DB_PASSWORD = '';
// Just an example of having multiple databases, so you can just Database::DB_1 when you need to use them
const DB_1 = '';
const DB_2 = '';
const DB_3 = '';
public function __construct($db = self::DB_1, $host = self::DB_HOST, $username = self::DB_USERNAME, $password = self::DB_PASSWORD) {
$this->db = $db;
$this->host = $host;
$this->username = $username;
$this->password = $password;
$this->db = $db;
}
// So if you have different databases, you can create different functions to connect to them via PDO drivers
public function connectToMySQL($db = null) {
$dsn = is_string($db) ? 'mysql:dbname='.$db.';host='$this->host : 'msql:dbname='.$this->db.';host='$this->host;
try {
return new PDO($dsn, $this->username, $this->password);
} catch (PDOException $E) {
echo 'Connection error: '.$E->getMessage();
exit();
}
}
To use this you would just:
/*
* Remeber how we defined it? you can leave the parameters blank, or pass in things
*/
$Database = new Database();
/*
* A PDO database object that connects to your database automaticaly.
* You can also passin Database::DB_2 sand stuff if you hav multiple databases.
* is a PDO object, so to use it, just look up PHP's PDO tutorials
*/
$PDO = $Database->connectToMySQL();
/*
* Then to end the connection, it's just as simple as setting it to null
*/
$PDO = null;
This way, you create 1 Database object that can generate MANY connections, it's like a Factory class.
I believe this why is most versatile, but I'm always open to suggestions as well.
I have a class called DB (class.pdo.php) that does all the handling on mysql queries using PDO and another class called user that I use to manage a login system.
My question relates to always having to instantiate the $db in every public function of users so I can use DB. Is this efficient? Shouldn't I be instantiating DB inside the __construct() of users?
This is my code
require_once("../../class.pdo.php");
class user {
private $db = null;
public function __construct(){
/* Empty? */
}
public function find_by_email($email){
$db = new db();
$db->query('SELECT * FROM users WHERE email = :email LIMIT 1');
$db->bind(':email',$email);
$result = $db->single();
return $result;
}
public function create($email,$password,$first_name,$last_name){
$db = new db();
$db->query("INSERT INTO users(email,password,first_name,last_name,created_at) VALUES (:email,:password,:first_name,:last_name,NOW())");
$db->bind(':email',$email);
$db->bind(':password',$password);
$db->bind(':first_name',$first_name);
$db->bind(':last_name',$last_name);
$result = $db->execute();
return $db->lastInsertId();
}
[more similar functions ommited]
Well, despite of some comments suggesting the use of the Singleton pattern, I totaly disagree in using it for this purpose.
Your application will not always use a single connection to just one database.
Let me show you how I'd do this:
class DbConnector {
private $dbh;
private $dsn;
public function __construct($dsn) {
$this->dsn = $dsn;
}
private function connect() {
if($this->dbh === null) {
$this->dbh = new PDO($this->dsn);
}
}
public function disconnect {
if($this->dbh !== null) {
$this->dbh = null;
}
}
public function query($sql) {
$this->connect();
//... do the rest
}
public function fetchAll($sql) {
$this->connect();
//... do the rest
}
public function insert($table, $values) {
$this->connect();
//... do the rest
}
public function update($table, $values, $cond) {
$this->connect();
//... do the rest
}
public function delete($table, $cond) {
$this->connect();
//... do the rest
}
}
class User {
private $dbConn;
public function __construct(DbConnector $dbConn) {
$this->dbConn = $dbConn;
}
public function create($email,$password,$first_name,$last_name){
$this->dbConn->query("INSERT INTO users(email,password,first_name,last_name,created_at VALUES (:email,:password,:first_name,:last_name,NOW())");
$this->dbConn->bind(':email',$email);
$this->dbConn->bind(':password',$email);
$this->dbConn->bind(':first_name',$email);
$this->dbConn->bind(':last_name',$email);
$this->dbConn->execute();
return $this->dbConn->lastInsertId();
}
// ...
}
Results:
No singleton used = testable.
Connection to the database is just openned when needed
Your connection is persistent. If you open and close connections in every method, you loose the capability of creating transactions.
What about using the Singleton pattern to create one object for the connection and use it everytime you need it, instead of creating new objects all the time?
I would do something similar with lazy loading: don't initiate in the constructor unless you're sure you actually need the connection every time an object is created but absolutly don't create a new object on each method call. Instead, save the resulting object into an object var which is checked on each method call and initiates the connection if missing.
class user {
protected $_db = null;
private function _init_db() { $this->_db = new XXX; }
public function create( $x, $y, $z ) {
if ( ! $this->_db ) $this->_init_db();
# use $this->_db ..
}
public function find_by_email( $x, $y, $z ) {
if ( ! $this->_db ) $this->_init_db();
# etc
}
}
This has the advantages of avoiding global static state (singletons..) and only creates the connection / object at the very last moment so you're sure you actually need it and it's not just a useless connection.
Speaking of efficiency, the main problem with your code is that it establishes new connection for the every method called. This one is indeed inefficient to the point of killing your database server. And it's incomparable to the other problem you have.
So, in general, you can have whatever way you want - either get somehow an instance of db class in the every function or use a class variable - but either way have to use single PDO instance throughout whole application.
Also I find your functions quite inefficient from the amount of code point of view, and would have optimized them this way
public function create($email,$password,$first_name,$last_name){
$sql = "INSERT INTO users(email,password,first_name,last_name,created_at) VALUES (?,?,?,?,NOW())";
$this->db->query($sql);
$result = $db->execute(func_get_args());
return $db->lastInsertId();
}
From a object point of view, I'd leave database instantiating within the methods, rather than an entire class.
Each method should only see the variables and data it needs, in order to perform its function.
For instance, a createUser() method would need to see variables or properties such as $username, $usergroupId, as well as $database etc.
However, you may have a function which is called randomPassword(), which generates a random password from numbers and letter.
This randomPassword() function doesn't need the database object and therefore, an already initialised database connection in the object scope would be wasteful.
It would be better only to create the new database object in methods that required it.
In addition, in my application, I don't create a new database connection each time I used new database. Instead, I've opted for a singleton PDO database object which keeps the connection active.
I can then just call the database object statically to retrieve an existing connection. Therefore, if, in the process of running my application I need to have 20 database objects, my application then only returns the same object, and the same connection.
So recently I've really started to use php actively, and I need some insights on different ways to use database connections.
At first I just used the simple mysql_connect():
<?php
$connection = mysql_connect(DB_HOST, DB_USER, DB_PASS) or die(mysql_error());
mysql_select_db(DB_DB, $connection);
?>
After a while I created a database class which I started to include and initialize in every file - something like this:
<?php
class MySQL_DB {
var $connection;
function MySQL_DB(){
$this->connection = mysql_connect(DB_HOST, DB_USER, DB_PASS) or die(mysql_error());
mysql_select_db(DB_DB, $this->connection);
}
function query($q){
$res = mysql_query($q, $this->connection) or die(mysql_error());
return $res;
}
}
$database = New MySQL_DB;
?>
And this is what I'm using at the time - and it's working fine - but there are always ways to improve.
So my question to you is how do you manage your database connections?
Do you use classes?
What does your classes contain (just
the connection or even functions?)
What practices do you recommend?
I recommend to use PDO. Don't reinvent the weel. It's a nice OO-interface to many database engines.
Additionally I create a small function which just inititializes PDO object. So all connection settings can be changed in one place.
Your current approach is pretty standard, and works well. I used it for a long time. It's true that modules like PDO provide base functionality like this now, which is very nice as well and can get you away from problems with home-brew code.
However, I've taken the connection management one step further. If you get into a complex application, you might get into a situation where you have multiple databases, or heavy database use. Including a single database connection file and having a global $database variable becomes unwieldy for multiple databases, and it's unnecessary for application requests that might not need a database connection. Remember, connecting to the database is expensive.
What I've done is create a singleton DatabaseManager class that handles the database object for me, and makes sure multiple connections to a given DB don't get instantiated. Instead of initializing a new database object at the top of your app, you simply call on the DatabaseManager every time you need the object.
$db = DatabaseManager::getDatabase();
Here's an example class that I had whipped up for a CodeIgniter project. You can see in the getDatabase() function it simply loads CodeIgniter's default database object, which you would substitute for your own class (and run the connection routine for it) if you weren't using CI. This is a pretty simplistic management class, and could be extended to manage multiple connections to different databases fairly easily.
<?php
/**
* Implements the Singleton pattern to prevent multiple instantiations and connections
* to the application database.
*
*/
class Database_manager
{
private static $instance;
public $db;
/**
* Constructor function is declared private to prevent instantiation.
*
*/
protected function __construct()
{
parent::__construct();
}
/**
* Returns an instance of a Database_manager.
*
* #return object Database_manager object
*/
public static function getInstance()
{
if (self::$instance == null) {
$className = __CLASS__;
self::$instance = new $className();
}
return self::$instance;
}
public static function getDatabase()
{
$instance = self::getInstance();
if ($instance->db == null) {
//utilize CodeIgniter's database loader
$instance->db = $instance->load->database('',true);
if (! is_object($instance->db)) throw new Exception("Could not load database.");
}
return $instance->db;
}
}
Perhaps the most common advantage I get out of using this style of connection management is when I have to take down an application for database maintenance. By not instantiating a database connection until I need it, I can easily put up a "maintenance in progress" message on a site (short circuiting normal MVC dispatching), and not worry about requests to the application opening a DB connection while maintenance is in progress.
Usage of classes are the way to go to increase customized re-usability.
Bring in all generic implementations into the class. You are on the right track.
This website has the following clean approach.
This website link is no longer present. Archive Link.
class connection {
// Possible Modules are as follows:
// DBX_MYSQL, DBX_ODBC, DBX_PGSQL, DBX_MSSQL, DBX_FBSQL, DBX_SYBASECT, DBX_OCI8, DBX_SQLITE
private $module = DBX_MYSQL;
private $host = "localhost";
private $database = "test";
private $username = "testuser";
private $password = "testpass";
private $link;
private $result;
public $sql;
function __construct($database=""){
if (!empty($database)){ $this->database = $database; }
$this->link = dbx_connect($this->module,$this->host,$this->database,$this->username,$this->password);
return $this->link; // returns false if connection could not be made.
}
function query($sql){
if (!empty($sql)){
$this->sql = $sql;
$this->result = dbx_query($this->link,$sql,DBX_RESULT_UNBUFFERED);
return $this->result;
}else{
return false;
}
}
function fetch($result=""){
if (empty($result)){ $result = $this->result; }
return dbx_fetch_row($result);
}
function __destruct(){
dbx_close($this->link);
}
}
In your database manager example, you did not define a parent for your class.
Therefore, invoking parent::__constructor() yields an exception,
and also, you cannot use the load property of code ignitor.
Which class did you use as an extension for your DatabaseManager?
Since i do not know where you placed your databasemanager code, nor which class you used as its parent, i circumvented the exceptions by making the getDatabase() method receive an input parameter which i called $loader.
Normally, this $loader object will be the model class requiring access to a database.
public static function getDatabase($loader)
{
$instance = self::getInstance();
if ($instance->db == null) {
//utilize CodeIgniter's database loader
$instance->db = $loader->load->database('default',true);
if (! is_object($instance->db)) throw new Exception("Could not load database.");
}
return $instance->db;
}
Best regards.