PHP Trivial Learning

• If you define __construct in a subclass, you do not call the parent class's __construct, and if you need to call the parent class's constructor at the same time, you need to use the parent::__construct () explicit call.

1 classCar {2 function __construct () {3Print"Parent class constructor is called \ n";4    }5 }6 classTruck extends Car {7 function __construct () {8Print"The subclass constructor is called \ n";9 parent::__construct ();Ten    } One } A$car =NewTruck ();

• Inside the class: Call property itself property $this->name and static self :: $name

• If the constructor is defined as a private method, it is not allowed to instantiate the object directly, which is typically instantiated by a static method, which is often used in design mode to control the creation of objects, such as a singleton pattern that only allows a globally unique object.

1 classCar {2     Private function__construct () {3         Echo' Object create ';4     }5 6     Private Static $_object=NULL;7      Public Static functiongetinstance () {8         if(Empty(Self::$_object)) {9Self::$_object=NewCar ();//internal methods can call private methods, so you can create objects hereTen         } One         returnSelf::$_object; A     } - } - //$car = new Car ();//Do not allow direct instantiation of objects here the $car= Car::getinstance ();//using static methods to obtain an instance

• Overload
  • The overloads of a property are implemented by __set,__get,__isset,__unset to assign, read, and determine whether a property is set or destroyed, respectively, for a nonexistent property.
  • The overloads of the method are implemented by __calL, and when a non-existent method is called, the __call method is called, and the __callstatic overload is used when a static method that does not exist is called.

• Serialization of objects
  
  • objects can be serialized as strings by the Serialize method, used to store or pass data, and then deserialized into objects using unserialize when needed.

1 classCar {2      Public $name= ' car ';3 }4 $a=NewCar ();5 $str=Serialize($a);//object is serialized into a string6 Echo $str.‘ <br> ';7 $b=unserialize($str);//Deserializing Objects8 Var_dump($b);

• What's the difference between a single quote and a double quote?
  • 　　

    PHP allows us to include it directly in a double quote string 字串变量 .

    The contents of a single quote string are always considered ordinary characters.

    Like what:

    $str = ' Hello '; echo "str is $STR"; Operation Result: STR is Helloecho ' str is $str '; Operation Result: STR is $STR

PHP Trivial Learning