PHP functions class and object functions

PHP is a widely used server-side scripting language. Its wide application is mainly due to its powerful function library. This article will introduce the class and object functions of functions in PHP.

In PHP function libraries, it is very common to use classes. A class defines all the properties and methods of an object, which makes the code more structured and organized. In PHP, a class is defined through the class keyword. The following is an example of a simple PHP class definition:

class MyClass {
  // 属性定义
  public $prop1 = "I'm a class property!";
 
  // 方法定义
  public function setProperty($newval) {
      $this->prop1 = $newval;
  }
 
  public function getProperty() {
      return $this->prop1 . "<br />";
  }
}

In the above code, we define a class called MyClass and have a property named prop1 and two named setProperty() and getProperty() method. You need to use the $this keyword when assigning properties and calling methods.

Next we can create an instance of MyClass and access its properties and methods:

$obj = new MyClass;

echo $obj->prop1; // 输出 "I'm a class property!"

$obj->setProperty("I'm a new property value!");

echo $obj->getProperty(); // 输出 "I'm a new property value!"

In the above code, we create an instance named $obj and use $ The obj->prop1 syntax accesses the value of a class property. Next, we call the setProperty() method to modify the value of the prop1 property. Finally, we call the getProperty() method again to see the new value of the prop1 property.

In addition to ordinary PHP classes, there is also a special type of class called an abstract class. Abstract classes cannot be instantiated and are only used to derive other classes. Methods in abstract classes may or may not contain implementations. If a method is declared abstract, then derived classes must implement that method. The following is a simple PHP abstract class definition example:

abstract class AbstractClass {
    // 强制要求子类定义这些方法
    abstract protected function getValue();
    abstract protected function prefixValue($prefix);
 
    // 普通方法
    public function printOut() {
        print $this->getValue() . "<br/>";
    }
}

In the above code, we create an abstract class named AbstractClass and define two named getValue() and prefixValue() abstract method. Next, we define a normal method called printOut(). Abstract methods in a class can be overridden by any subclass that implements that class.

In addition to ordinary PHP classes and abstract classes, PHP also provides a special type of class called an interface. Interfaces are similar to abstract classes, but they cannot contain any implementation, only method signatures. A class can implement one or more interfaces, and when implementing an interface, it must implement all methods declared in the interface. The following is a simple PHP interface definition example:

interface MyInterface {
    public function getValue();
    public function setValue($value);
}

In the above code, we create an interface named MyInterface and define two methods getValue() and setValue(). In the class that implements this interface, these two methods must be implemented.

Summary: Among the class and object functions of PHP functions, class is a commonly used concept in PHP function libraries. Classes in PHP can define properties and methods, which makes the code more structured and organized. Abstract classes and interfaces are special types of classes. In abstract classes, methods may contain implementation or not, while in interfaces, methods contain only method declarations. When implementing an abstract class or interface, all methods declared in it must be implemented.

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