Below is my base class i.e database methods.
// Constructor
public function __construct($argHost, $argUsername, $argPassword, $argDatabase)
{
$this->_host = $argHost;
$this->_username = $argUsername;
$this->_password = $argPassword;
$this->_database = $argDatabase;
}
// Connect to the database
public function Connect()
{
if (!$this->Is_Connected()) {
$this->_connection = mysqli_connect($this->_host,$this->_username,$this->_password,$this->_database);
} else {
return $this->_connection;
}
}
// Run query
public function Run($query)
{
if ($this->result = mysqli_query($this->_connection,$query)) {
return $this->result;
} else {
die("Couldn't perform the request");
}
}
And my child class is categories method below
class Categories extends Database
{
public $category_id = '';
public $category_name = '';
public $category_image = '';
// View Category
public function ViewCategories()
{
return $this->Run("SELECT * FROM categories");
}
}
Now the problem is that when i am running the Run() method by creating object of the base class it is working fine. But when i am creating object object the child class i.e categories and executing the method viewCategories(); i m receiving below errors
Warning: Missing argument 1 for Database::__construct(), called in E:\xampplite\htdocs\ecommerce\index.php on line 16 and defined in E:\xampplite\htdocs\ecommerce\classes\class.database.php on line 17
Warning: Missing argument 2 for Database::__construct(), called in E:\xampplite\htdocs\ecommerce\index.php on line 16 and defined in E:\xampplite\htdocs\ecommerce\classes\class.database.php on line 17
Warning: Missing argument 3 for Database::__construct(), called in E:\xampplite\htdocs\ecommerce\index.php on line 16 and defined in E:\xampplite\htdocs\ecommerce\classes\class.database.php on line 17
Warning: Missing argument 4 for Database::__construct(), called in E:\xampplite\htdocs\ecommerce\index.php on line 16 and defined in E:\xampplite\htdocs\ecommerce\classes\class.database.php on line 17
Warning: mysqli_query() expects parameter 1 to be mysqli, null given in E:\xampplite\htdocs\ecommerce\classes\class.database.php on line 35 Couldn't perform the request
Udated : This is how i am calling the methods
<?php
function __autoload($class_name) {
include 'classes/class.'.$class_name . '.php';
}
$connection = new Database("localhost", "raheel", "raheel786", "ecommerce");
$connection->Connect();
?>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Ecommerce</title>
</head>
<body>
<?php
$category = new Categories();
$category_list = $category->ViewCategories();
var_dump($category_list);
?>
</body>
</html>
Kindly help me how to fix that.
In your case you need to overload constructor. Just add empty __construct() method to child class
class Categories extends Database{
public function __construct() {}
...
}
but it will not solve your problem:)
As a solution i can see 2 variants:
1) make static variable _connection so it will be available in all objects
public function Connect(){
if( ! self::$_connection){
self::$_connection = mysqli_connect($this->_host,$this->_username,$this->_password,$this->_database);
}
return self::$_connection;
}
public function Run($query){
if($this->result = mysqli_query(self::$_connection,$query)){
return $this->result;
}
else
die("Couldn't perform the request");
}
2) I think it is better way. Make 2 independent classes with connect and queries so one will contain another
class Database {
// Constructor
public function __construct($argHost,$argUsername,$argPassword,$argDatabase){
$this->_host = $argHost;
$this->_username = $argUsername;
$this->_password = $argPassword;
$this->_database = $argDatabase;
}
// Connect to the database
public function Connect(){
if(!$this->Is_Connected()){
$this->_connection = mysqli_connect($this->_host,$this->_username,$this->_password,$this->_database);
} else {
return $this->_connection;
}
}
// Run query
public function Run($query){
if($this->result = mysqli_query($this->_connection,$query)){
return $this->result;
}
else
die("Couldn't perform the request");
}
}
class Categories extends Database{
private $db;
public function __construct(Database $db) {
$this->db = $db;
}
public $category_id = '';
public $category_name = '';
public $category_image = '';
// View Category
public function ViewCategories() {
return $this->db->Run("SELECT * FROM categories");
}
}
So usage is:
$connection = new Database("localhost", "raheel", "raheel786", "ecommerce");
$connection->Connect();
$category = new Categories($connection);
Attention! I didn't test it, just give an example
You shouldn't use inheritance for has-a relationship, inheritance describes the is-a relationship. And in your case Categories is not a Database, Categories has a database.
Use composition instead:
class Categories
{
private $database;
function __construct(Database $database)
{
$this->database = $database;
}
public function ViewCategories()
{
return $this->database->Run("SELECT * FROM categories");
}
}
And the usage:
$connection = new Database("localhost", "raheel", "raheel786", "ecommerce");
$connection->Connect();
// ...
$category = new Categories($connection);
$category_list = $category->ViewCategories();
var_dump($category_list);