Advanced feature analysis of PHP objects, patterns and practices
The examples in this article describe the advanced features of PHP object-oriented programming. Share it with everyone for your reference, as follows:
Advanced features
include:
1. Static methods and properties (access data and functions through classes instead of objects)
2. Abstract classes and interfaces (separation of design and implementation )
3. Error handling (exceptions)
4. Final classes and methods (restricted inheritance)
5. Interceptors (automatic delegation)
6. Destructor methods (cleanup before object destruction)
7. Clone objects (create A copy of the object)
8. Parse the object into a string
PS, learn to look at the code from the perspective of memory. Imagine the microscopic world of computers.
Small example of static method
<?php
class StaticExample{
static public $aNum = 10;
static public function sayHello(){
print "hello";
}
}
print StaticExample::$aNum."<br/>";
StaticExample::sayHello();
tips:
1. Static methods cannot access ordinary properties in a class because those properties belong to an object, but static properties can be accessed.
2. We cannot call static methods in objects, so we cannot use the pseudo variable $this in static methods.
Big example of static method
<?php
class ShopProduct{
private $title;
private $producerMainName;
private $producerFirstName;
protected $price;
private $discount = 0;
private $id = 0;
function __construct($title,$firstName,$mainName,$price){
$this->title = $title;
$this->producerFirstName = $firstName;
$this->producerMainName = $mainName;
$this->price = $price;
}
public function setID($id){
$this->id = $id;
}
public static function getInstance($id,PDO $pdo){
$query = "select * from products where id= '$id'";
$stmt = $pdo->query($query);
$row = $stmt->fetch();
if(empty($row)){
return null;
}
if($row['type'] == "book"){
$product = new BookProduct($row['title'],
$row['firstname'],
$row['mainname'],
$row['price'],
$row['numpages']
);
}else if($row['type'] == "cd"){
$product = new CdProduct($row['title'],
$row['firstname'],
$row['mainname'],
$row['price'],
$row['playLength']
);
}else{
$product = new ShopProduct($row['title'],
$row['firstname'],
$row['mainname'],
$row['price']
);
}
$product->setId($row['id']);
$product->setDiscount($row['discount']);
return $product;
}
public function getProducerFirstName(){
return $this->producerFirstName;
}
public function getProducerMainName(){
return $this->producerMainName;
}
public function setDiscount($num){
$this->discount = $num;
}
public function getDiscount(){
return $this->discount;
}
public function getTitle(){
return $this->title;
}
public function getPrice(){
return ($this->price - $this->discount);
}
function getProducer(){
return $this->producerFirstName." ".$this->producerMainName;
}
function getSummaryLine(){
$base = "$this->title({$this->producerMainName},";
$base .= "{$this->producerFirstName})";
return $base;
}
}
class CdProduct extends ShopProduct{
private $playLength;
function __construct($title,$firstName,$mainName,$price,$playLength){
parent::__construct($title,$firstName,$mainName,$price);//继承父类的构造函数
$this->playLength = $playLength;
}
function getPlayLength(){
return $this->playLength;
}
function getSummaryLine(){
$base = parent::getSummaryLine();
$base .= ":playing time {$this->playLength}";
return $base;
}
}
class BookProduct extends ShopProduct{
private $numPages = 0;
function __construct($title,$firstName,$mainName,$price,$numPages){
parent::__construct($title,$firstName,$mainName,$price);
$this->numPages = $numPages;
}
function getnumPages(){
return $this->numPages;
}
function getSummaryLine(){
$base = parent::getSummaryLine();
$base .= ":page count {$this->numPages}";
return $base;
}
}
$dsn = "sqlite:C:/Users/Administrator/Desktop/shop.db";
$pdo = new PDO($dsn,null,null);
$pdo->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);
$obj = ShopProduct::getInstance(1,$pdo);
echo $obj->getSummaryLine();
I hope this article will be helpful to everyone in PHP programming. For more related content, please pay attention to the PHP Chinese website (www.php.cn)!
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