php object-oriented tutorial 3

5. How to instantiate an object
We said above that the unit of an object-oriented program is an object, but an object is instantiated through a class. Since our class
will be declared, the next step is to instantiate it. object.
After defining the class, we use the new keyword to generate an object.

$对象名称= new 类名称（）；
<?php
class Person
{
//下面是人的成员属性
var $name; //人的名字
var $sex; //人的性别
var $age; //人的年龄
//下面是人的成员方法
function say() //这个人可以说话的方法
{
echo "这个人在说话";
}f
unction run() //这个人可以走路的方法
{
echo "这个人在走路";
}
}
$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 object name of our instance. Similarly, $p2, $p3
are also the object names of our instance. , a class can instantiate multiple objects, and each object is independent. The above code is equivalent to 3 people being instantiated. There is no connection between each person, which can only mean that they are all human beings. Everyone has their own surname
, gender and age attributes. Everyone has a way to talk and walk. As long as it is the member attribute and member
method reflected in the class, it is 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. When running
, they must be loaded into memory for use. Then objects How is it reflected in the memory? Logically speaking, memory is generally divided into 4 segments, stack space segment, heap space segment, code segment, and initialization static segment. Different declarations in the program are placed in different memory segments. The stack space segment It is a place to store data types that occupy the same space length and take up small space, such as integers 1, 10,
100, 1000, 10000, 100000, etc. The space occupied in the memory is the same length, both are 64 bit 4 bytes. So the data
is of variable length and takes up a lot of space. Which segment of the memory should be placed in it? Such data is placed in
heap memory. Stack memory can be directly accessed, while heap memory cannot be directly accessed. For our object,
number is a large data type and it takes up a variable length of space. Therefore, the object is placed in the heap, but the object name
is placed in the stack. In this way, The object name can be used.

$p1=new Person();

, please see the picture below for details:
As you can see from the picture above, $p1=new Person(); the right side of the equal sign is the real object instance, which is in the heap memory Entity, as shown in Figure 1

, there are 3 times of new Person(), so 3 spaces will be opened in the heap and 3 instance objects will be generated. 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 a space of its own will be created in the heap.
Each instance object in the heap stores attributes. For example, the instance objects in the heap now store name, gender,
and age. Each attribute in turn has an address.
$p1=new Person(); The right side of the equal sign $p1 is a reference variable. The first address of the object is assigned
to the reference variable "$p1" through the assignment operator "=", so $p1 It is a variable that stores the first address of the object. $p1 is placed in the stack memory. $p1 is equivalent to a pointer pointing to the object in the heap, so we can operate the object through the reference variable $p1. Usually we also call it an object. Reference
to the object.
6. How to use the members in the object
As seen above, there are two types of members in the PHP object, one is the member attribute and the other is the member method. We can now declare the object
, $p1=new Person(); how to use the members of the object? If you want to access the members of the object, you must use a special operator "->" to complete the access of the object members:
Object->Attribute $p1->name; $p2-> ;age; $p3->sex;
Object->Method $p1->say(); $p2->run();
As an example below:

<?php
class Person
{
//下面是人的成员属性
var $name; //人的名字
var $sex; //人的性别
var $age; //人的年龄
//下面是人的成员方法
function say() //这个人可以说话的方法
{
echo "这个人在说话";
}f
unction run() //这个人可以走路的方法
{
echo "这个人在走路";
}
}
$p1=new Person(); //创建实例对象$p1
$p2=new Person(); //创建实例对象$p2
$p3=new Person(); //创建实例对象$p3
//下面三行是给$p1对象属性赋值
$p1->name=”张三”;
$p1->sex=”男”;
$p1->age=20;
//下面三行是访问$p1对象的属性
echo “p1对象的名字是：”.$p1->name.”<br>”;
echo “p1对象的性别是：”.$p1->sex.”<br>”;
echo “p1对象的年龄是：”.$p1->age.”<br>”;
//下面两行访问$p1对象中的方法
$p1->say();
$p1->run();
//下面三行是给$p2对象属性赋值
$p2->name=”李四”;
$p2->sex=”女”;
$p2->age=30;
//下面三行是访问$p2对象的属性
echo “p2对象的名字是：”.$p2->name.”<br>”;
echo “p2对象的性别是：”.$p2->sex.”<br>”;
echo “p2对象的年龄是：”.$p2->age.”<br>”;
//下面两行访问$p2对象中的方法
$p2->say();
$p2->run();
//下面三行是给$p3对象属性赋值
$p3->name=”王五”;
$p3->sex=”男”;
$p3->age=40;
//下面三行是访问$p3对象的属性
echo “p3对象的名字是：”.$p3->name.”<br>”;
echo “p3对象的性别是：”.$p3->sex.”<br>”;
LAMP 大讲堂PHP 面向对象技术（全面讲解）
echo “p3对象的年龄是：”.$p3->age.”<br>”;
//下面两行访问$p3对象中的方法
$p3->say();
$p3->run();
?>

It can be seen from the above example that only the members in the object must be accessed using the object->properties and object->methods. There is no
second method to access the members in the object


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