PHP Single-instance mode

Singleton pattern Concept Singleton mode refers to the design pattern of a class with only one object instance in the whole application. Characteristics of the Singleton model

• A class has only one instance in the entire application
• Class must create this instance on its own
• This instance must be provided to the entire system on its own

The reason for using singleton mode in PHP I use PHP most of the operation is to deal with various databases, including Mysql,redis,memcache and other relational and non-relational database, so there will be a large number of connection database operations in an application, if not a singleton mode, It's always new, but each time new will consume a lot of memory resources and system resources, and each time you open and close the database connection is a great test and waste of the database. Post the bad database connection code I used to give you a demonstration of the error:

2. <?php
4. Class Mysqlconn
6. {
8. //MySQL database connection information
10. Const MYSQLHOSTNAME = "127.0.0.1";
12. Const Mysqlusername = "root";
14. Const MYSQLPASSWORD = "* * *";
16. Const MYSQLDBNAME = "Test";
18. Const Mysqlcharset = "UTF8";
22. /** 
24. * Description:mysql Database connection function
26. * Return value: Connection successfully returned to database connection handle; Connection failure returned error message
28. */
30. Public function Mysqlconnect ()
32. {
34. $db = new Mysqli (Self::mysqlhostname, Self::mysqlusernaem, Self::mysqlpassword, self::mysqldbname); //Connect to database
36. $db->set_charset (self::mysqlcharset);
38. if (Mysqli_connect_errno ())
40. {
42. throw New Circlemysqlexception ("Server system Failure", 1001);
44. }
46. Else
48. {
50. return $db;
52. }
54. }
56. }

BUG: Each database connection should be new to this class, then call the Mysqlconnect method, return close, frequent new and database connection close operations are very resource-intensive

Improved:

Each time you should return directly to the database connection handle that is already open in the current app

1. Singleton mode returns database connection handle
2. $db = Mysqlconn::singlemysqlconnect ();

Implementation of PHP single-instance mode

2. <?php
4. Class Singleton
6. {
8. /** 
10. * Description: (1) static variable, save global instance, bind to class, independent of Object
12. * (2) Private attribute, in order to avoid calling class name directly outside of class:: $instance, prevent null
14. */
16. private static $instance;
20. /** 
22. * Description: Database connection handle
24. */
26. private $db;
30. /** 
32. * Description: Privatization of constructors to prevent external instantiation of objects
34. */
36. private static function __construct ()
38. {
40. }
44. /** 
46. * Description: Privatization of cloning functions to prevent external cloning of objects
48. */
50. Private function __clone ()
52. {
54. }
58. /** 
60. * Description: Static method, single access unified portal
62. * @return Singleton: Returns the unique object instance in the app
64. */
66. public static function getinstance ()
68. {
70. if (! ( Self::$instance instanceof Self))
72. {
74. Self::$instance = new self ();
76. }
78. return self::$instance;
80. }
84. /** 
86. * Description: Gets the connection handle of the private method of the database
88. */
90. Public function Getdbconnect ()
92. {
94. return $this->db;
96. }
98. }

• Requires a static member variable that holds a unique instance of the class (usually $instance as a private variable)
• Constructors and clone functions must be declared private, in order to prevent the external program new class from losing the singleton schema meaning
• You must provide a public static method that accesses this instance, which returns a reference to the unique instance

PHP Single-instance mode