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Detailed explanation of usage examples of __get and __set in PHP

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Release: 2016-08-08 09:19:27
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php object-oriented _get(), _set() usage
Generally speaking, always define the attributes of a class as private, which is more in line with realistic logic. However, reading and assigning operations to attributes are very frequent, so in PHP5, two functions "__get()" and "__set()" are predefined to obtain and assign attributes. It is similar to the operation of javabean in java, and the method used is similar, except that there is no need to perform set and get operations on each field like in javabean. Just add two magic methods. That is, the operations of setting and obtaining values ​​of private members. PHP5 provides us with special methods for setting and obtaining values ​​for attributes, the two methods "__set()" and "__get()". These two methods do not exist by default, but we add them to the class manually. Inside, like the constructor method (__construct()), it will only exist if it is added inside the class. You can add these two methods in the following way, and of course you can also add them according to your personal style:

Copy Code The code is as follows:


//__set() method is used to set private properties
public function __set($name,$value){
$this->$name = $value;
}
//__get () method is used to get private attributes
public function __get($name){
return $this->$name;
}


__get() method: This method is used to get private member attribute values, there are A parameter, the parameter is passed in the name of the member attribute you want to obtain, and the obtained attribute value is returned. We do not need to call this method manually, because we can also make this method a private method, which directly obtains the private attribute. The object is automatically called at that time. Because the private property has been encapsulated, the value cannot be obtained directly. However, if you add this method to the class, you will automatically obtain the value directly when using a statement such as "echo$p1->name". Call the __get($name) method and pass the attribute name to the parameter $name. Through the internal execution of this method, the value of the private attribute we passed in is returned. If the member properties are not encapsulated as private, the object itself will not automatically call this method.
__set() method: This method is used to set values ​​for private member attributes. It has two parameters. The first parameter is the name of the attribute you want to set the value for, and the second parameter is the value you want to set for the attribute. , no return value. This method also does not need to be called manually. It can also be made private. It is automatically called when directly setting the private attribute value. The same private attribute has been encapsulated
. If there is no __set() Methods are not allowed, for example: $this->name='zhangsan', this will cause an error, but if you add the __set($property_name, $value) method to the class, you can directly set the private property When assigning a value, it will be automatically called, passing the attribute such as name to $property_name, and passing the value "zhangsan" to be assigned to $value. Through the execution of this method, the purpose of assignment is achieved. If the member properties are not encapsulated as private, the object itself will not automatically call this method. In order not to pass in illegal values, you can also make a judgment in this method. The code is as follows:

Copy the code The code is as follows:


class Person
{
//The following are the member attributes of the person, which are all encapsulated private members
private $name; // Person's name
private $sex; //Person's gender
private $age; //Person's age
//__get() method is used to obtain private properties
private function __get($property_name)
{
echo "In When directly obtaining the private property value, the __get() method is automatically called
";
if(isset($this->$property_name))
{
return($this->$property_name) ;
}
else
{
return(NULL);
}
}
//__set() method is used to set private properties
private function __set($property_name, $value)
{
echo "Set private properties directly When the value is set, the __set() method is automatically called to assign a value to the private property
";
$this->$property_name = $value;
}
}
$p1=newPerson();
// Directly assigning values ​​to private attributes will automatically call the __set() method for assignment
$p1->name="张三";
$p1->sex="male";
$p1->age =20;
//Get the value of the private attribute directly, the __get() method will be automatically called to return the value of the member attribute
echo "Name:".$p1->name."
";
echo "Gender:".$p1->sex."
";
echo "Age:".$p1->age."
";
?>


Program execution result:
When directly setting the value of a private attribute, this __set() method is automatically called to assign a value to the private attribute
When directly setting the value of a private attribute, this method is automatically called_ The _set() method assigns values ​​to private attributes
When directly setting the value of a private attribute, this __set() method is automatically called to assign a value to a private attribute
When directly obtaining the value of a private attribute, this method is automatically called_ _get() method
Name: Zhang San
When directly obtaining the private attribute value, this __get() method is automatically called
Gender: Male
When directly obtaining the private attribute value, This __get() method is automatically called
Age: 20

If the above code does not add the __get() and __set() methods, the program will error because private members cannot be operated outside the class , and the above code helps us directly access the encapsulated private members by automatically calling the __get() and __set() methods.

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