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The difference between static attributes and static methods in php
The difference between static attributes and static methods in php
This article mainly introduces the detailed explanation of the difference between PHP static properties and static methods. Friends who need it can refer to
static
public, private, protected
Static properties
Adding the static keyword before a property or method is a static property
In actual work, there will be multiple objects of a class , a copy of the data may be shared.
Solution:
1: Class constant, cannot be changed.
Example:
2: Sometimes after sharing a piece of data, all objects sharing this data must also allow changes.
So there is static
Syntax:
Example:
Tip: Static properties are similar (identical) to class constants. The only difference is that class constants cannot be changed, while static properties can be changed. The access method is the same.
:: You can only access class constants, static properties, and static methods
Static properties need to add $. There is no $ before the constant name, so you don’t need to add it at all when accessing class constants.
-> There is no need to add $
static method
Add static before the method, it is a static method
Access to static members: Access to static properties
Public static properties are accessed outside the class:
Syntax:
Class name::static Property name
Access all static properties within the class
##Static method access
Outside-class accessSyntax: Static method exists in class space. Class name::Method name();
##Intra-class access:
Syntax:
self: :Method name();
Static properties are saved in the class space, non-static properties Saved in the object space
Static properties are accessed through class access(::), non-static properties are accessed through object(->)
Static methods are accessed through class access( ::),
If a method does not operate the properties belonging to the object space internally, it will be encapsulated into a static method and called through the class. This method will be much faster.
$this cannot appear in static methods
*******##Important note:
If it belongs to a class, use the class name or self::, if it belongs to an object, use the object name or $this->. (Except ordinary methods==>Although ordinary methods belong to the class space, they still need to be accessed using $this or the object name)Magic method
php output statement:echo A grammar structure can only output the scalar data type, and there is no output for Boolean value. The value false has no outputprint_r() Not only can it output scalar data types, it can also output data. There is no output for the boolean value falsevar_dump($v1,$v2); More output variables The information is mainly for programmers to debug programs using __tostring(); When echoing an object, it means converting a structure into a string. __tostring() magic method is called by the PHP automatic execution mechanism when an object is to be converted into a string due to a certain operation. This method is to capture errors (Fatal Erorr fatal errors) and output a prompt message Example:
__clone();
clone(); Clone function
thinkphp3.2.3 registration Upload pictures
thinkphp3.2.3 complete paging example
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