PHP single-case mode (duty mode)

Simply put, an object (before learning design patterns, need to understand the object-oriented thinking) is only responsible for a specific task;

Singleton class:

1. The constructor needs to be marked as private (access control: Prevent external code from creating objects using the new operator), the Singleton class cannot be instantiated in other classes, and can only be instantiated by itself;

2. Have a static member variable that holds an instance of the class

3, has a public access to this instance of the static method (common getinstance () method to instantiate a singleton class, through the instanceof operator can detect whether the class has been instantiated)

In addition, you need to create a __clone () method to prevent the object from being copied (cloned)

<?php/** * Created by Phpstorm. * User: * date:2017/1/2 * Time: PM 3:32 */class Single {    ///save private static instance variable for instance private    $instance;    The private tag is constructed in a way that instantiates the    private function __construct () {        echo "This is construct function")    by other means;    The Clone method is created to prevent the cloned public    function __clone () {        trigger_error ("clone was not allowed", e_user_error);    }    A singleton method, a public static method that the user accesses to an instance, publicly    static function shareinstance () {        //instanceof: Determines whether the instance is an instance of self or a subclass        if (! ( Self:: $instance instanceof self) {self            :: $instance = new self ();        }        Return self:: $instance;    }}

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trigger_error()The function creates a user-level error message.

trigger_error()The function can be associated with a built-in error handler, or you can use a user-defined function as a new error handler (Set_error_handler ()).

Trigger_error (Errormsg,errortype);

Parameters	Description
ErrorMsg	Necessary. Specifies the error message. The maximum length is 1024 bytes.
ErrorType	Optional. Specifies the type of error. Possible values: E_user_errore_user_warninge_user_notice (default)

Simply put, an object (before learning design patterns, need to understand the object-oriented thinking) is only responsible for a specific task;

Singleton class:

1. The constructor needs to be marked as private (access control: Prevent external code from creating objects using the new operator), the Singleton class cannot be instantiated in other classes, and can only be instantiated by itself;

2. Have a static member variable that holds an instance of the class

3, has a public access to this instance of the static method (common getinstance () method to instantiate a singleton class, through the instanceof operator can detect whether the class has been instantiated)

In addition, you need to create a __clone () method to prevent the object from being copied (cloned)

<?php/** * Created by Phpstorm. * User: * date:2017/1/2 * Time: PM 3:32 */class Single {    ///save private static instance variable for instance private    $instance;    The private tag is constructed in a way that instantiates the    private function __construct () {        echo "This is construct function")    by other means;    The Clone method is created to prevent the cloned public    function __clone () {        trigger_error ("clone was not allowed", e_user_error);    }    A singleton method, a public static method that the user accesses to an instance, publicly    static function shareinstance () {        //instanceof: Determines whether the instance is an instance of self or a subclass        if (! ( Self:: $instance instanceof self) {self            :: $instance = new self ();        }        Return self:: $instance;    }}

Report

trigger_error()The function creates a user-level error message.

trigger_error()The function can be associated with a built-in error handler, or you can use a user-defined function as a new error handler (Set_error_handler ()).

Trigger_error (Errormsg,errortype);

Parameters	Description
ErrorMsg	Necessary. Specifies the error message. The maximum length is 1024 bytes.
ErrorType	Optional. Specifies the type of error. Possible values: E_user_errore_user_warninge_user_notice (default)