Summary of common PHP magic methods. Common magic methods include __tostring () _ Call () _ autoLoad () _ clone () _ GET () _ SET () _ isset () _ unset () 1. _ Tostring () is used to define the reference of the output object. it is often used to print out a commonly used magic method: __tostring () _ Call () _ autoLoad () _ clone () _ GET () _ SET () _ isset () _ unset ()
1. _ Tostring () is used to define the reference value of an output object. it is often called to print information of some objects and must return values.
Eg: there is a persion class
Persion per = new persion ()
Echo per; // an error occurs when calling directly.
We can add the _ tostring () method to the class definition.
Function _ Tostring ()
{
$ Str = this-> $ name. this-> age;
Return $ str;
}
2. _ clone () object replication
Reference assignment
$ Per1 = $ per2; this has only one address in the memory.
$ Per1 = clone $ per2 has two memory addresses.
3. the _ call () method is automatically executed when a function that does not exist in the class instance is called.
If you try to call a function that does not exist in the class, a syntax error occurs.
We can declare the Call () method in the class;
Function _ call ($ funName, $ argu)
{
Echo "the function named". $ funName. "parameter is". printf ($ argh). "does not exist ",
}
4. _ autoLoad: automatically loaded class files used. This function is added on the reference page.
We have used this case. to call other PHP files on the page, we need to use the include method.
However, if there are dozens of pages that need to be referenced, it is too cumbersome. we can use the autoload method in this page.
Function _ autoload ($ className)
{
Include $ className. ". php ";
}
In this way, all references to other classes will automatically reference this class of files. the prerequisite class file name must be class name. php
5. Private attributes in the _ GET () objects class
If a property in a class is set to a private property, it cannot be accessed in the class instance, but how can this be accessed?
We can use _ GET ()
Eg:
Class
Class person
{
Private $ name;
Private $ age;
}
Instantiate person per = new person ()
Per-> $ name; // The value cannot be obtained.
However, if we add the _ GET method to the class
Function _ GET ($ proName)
{
Return this-> $ proName;
}
We can call Per-> $ name again to access it.
In this case, some people may ask questions. what is the difference between directly accessing private variables and making them public?
If it is declared public, we can read it at will. if it is private, if we add the get method, the GET method will be called every time the private attribute is called, in this way, we can add some logic processing in the get method.
6. _ SET (): SET the private attribute www.2cto.com in the class.
The principle is the same as above. we can add the _ SET () function to the class. every time a value is assigned to a private attribute by calling the class instance, the _ SET function is executed. the Function prototype is as follows:
Function _ SET ($ proName, $ value)
{
This-> $ proName = $ value;
}
Since it is a method assignment, we can do some logic processing.
7. _ isset () is automatically called when the private attribute or method in the class exists
First, we will first introduce the isset method, which is used to determine whether the attributes and methods exist, but we cannot determine whether a private attribute in the class exists through the class instance.
If we use isset (per-> $ name); // the returned value is false, but the $ name attribute does exist, how can this problem be solved?
Solution:
1. Define $ name as a private property
2.
Add in class definition
Function _ isset ($ proName)
{
Return isset (this-> $ proName); // you can access private attributes within the class.
}
In this case, we call isset ($ name) again; the return value is true;
8. _ unset () is automatically called when private variables in the class are cleared.
In combination, the unset () unset method can delete attributes. when we need to delete attributes in a class, if it is a public attribute, we can directly
Delete, but if it is private, we can't implement it by using this method.
How to implement it? we can use the _ unset () method to implement this function. we need to add
Function _ unset ($ proName)
{
Unset (this-> $ proName );
}
Now we can call unset ($ name); to delete the private attribute $ name in the person class.
From the column jt521xlg
Aggregate () _ Call () _ autoLoad () _ clone () _ GET () _ SET () _ isset () _ unset () 1. _ Tostring () is used to define output object reference call is often used to print...
