php object-oriented (OOP) - instantiating objects

$Object name = new Class name();

class Person
{
//The following are the member attributes of the person
var $name; //The person’s name
var $ sex; //The person's gender
var $age; //The person's age
//The following is the person's member method
Function say() { //The method by which this person can speak
Echo "This person is talking";
}
function run() { //How this person can walk
  echo "This person is walking";
}
}
$p1=new Person();
$p2=new Person();
$p3= new Person();
?>

$p1=new Person();

This code is the process of generating instance objects through classes. $p1 is the name of the object we instance. Similarly, $ p2, $p3 are also the names of the objects we instantiate. A class can instantiate multiple objects, and each object is independent. The above code is equivalent to the instance of 3 people. There is no connection between each person. It can show that they are all human beings. Each one has his own name, gender and age attributes. Everyone has a way of talking and walking. As long as it is the member attributes and member methods reflected in the class, it is included in the instantiated object. It contains these properties and methods.

Objects in PHP, like integers and floating point types, are also a data class. They are used to store different types of data. They must be loaded into memory for use during runtime. Then the objects in the memory are How is it reflected? Logically speaking, memory is roughly divided into 4 segments, the stack space segment, the heap space segment, the code segment, and the initialized static segment. Different declarations in the program are placed in different memory segments. The stack space segment is used for storage. Data types of the same space length and occupying small space, such as integers 1, 10, 100, 1000, 10000, 100000, etc. occupy the same length of space in the memory, and are all 64 bits and 4 bytes. So where should the data of a data type that has a variable length and takes up a lot of space be placed in that memory segment? Such data is placed in the heap memory. Stack memory can be directly accessed, while heap memory cannot be directly accessed. For our object, it is a large data type and takes up space of a variable length. Therefore, the object is placed in the heap, but the object name is placed in the stack, so that the object can be used through the object name. .

$p1=new Person();

For this code, $p1 is the object name in the stack memory, and new Person() is the real object in the heap memory. Please see the figure below for details:

As you can see from the above picture, $p1=new Person(); the right side of the equal sign is the real object instance. The entity in the heap memory. There are 3 times of new Person() in the above picture, so it will be in the heap. It opens up 3 spaces and generates 3 instance objects. Each object is independent of each other and uses its own space. In PHP, as long as a new keyword appears, an object will be instantiated and placed on the heap. Create your own space inside.

Each instance object in the heap stores attributes. For example, the instance objects in the heap now all store name, gender and age. Each attribute in turn has an address.

$p1=new Person();$p1 on the left side of the equal sign is a reference variable. The first address of the object is assigned to the reference variable "$p1" through the assignment operator "=", so $p1 is the first address of the stored object. The address variable, $p1, is placed in the stack memory. $p1 is equivalent to a pointer pointing to an object in the heap, so we can operate the object through the reference variable $p1. Usually we also call the object reference an object.

The above content is quoted from Brother "Little Fried Peanuts", thank you for sharing.

The above has introduced PHP object-oriented (OOP)-instantiated objects, including aspects of it. I hope it will be helpful to friends who are interested in PHP tutorials.