Implementation code sharing of database singleton mode in PHP, php database

Implementation code sharing of database singleton mode in PHP, php database_PHP tutorial

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Release： 2016-07-13 10:20:26

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Implementation code sharing of database singleton mode in PHP, php database

First of all, we need to understand the concept of singleton mode. So what is singleton mode?

The singleton mode, as its name suggests, means that there is only one instance.

As an object creation mode, the singleton mode ensures that a certain class has only one instance, and it instantiates itself and provides this instance to the entire system. This class is called a singleton class.

There are three main points of the singleton pattern:

First, a class can only have one instance;
The second is that it must create this instance by itself;
Third, it must provide this instance to the entire system by itself.

Let’s discuss why we should use PHP singleton mode?

Most people understand its purpose from the literal meaning of the singleton pattern, thinking that it saves system resources, avoids repeated instantiation, and is a kind of "family planning". And PHP executes it every time All resources will be cleared from memory when the page is completed. Therefore, the singleton in PHP actually needs to be re-instantiated every time it is run, thus losing the meaning of repeated instantiation of the singleton. From this aspect alone It is said that PHP's singleton is indeed a bit disappointing to everyone. But does a singleton only have this function and application? The answer is no, let's take a look.

1. PHP is mainly used in database applications, so there will be a large number of database operations in an application. When developing in an object-oriented way (nonsense), if you use the singleton mode, you can avoid a lot of new operation consumption. resources.

2. If a class is needed to globally control certain configuration information in the system, it can be easily implemented using the singleton mode. This can be found in the FrontController part of zend Framework.

3. In a page request, it is easy to debug because all the code (such as database operation class db) is concentrated in one class. We can set hooks in the class and output logs to avoid var_dump and echo everywhere. .

class db {
  public static $cennct = null;
  private function __construct(){return false;}
  private function conn(){
    $pdo = new PDO('mysql:host=localhost;dbname=dbname','root','');
    $pdo->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, true);    
    $pdo->query('set names utf8');            
    return $pdo;                  
  }
  public static function getdb(){
    if(self::$cennct == null )
      self::$cennct = self::conn(); 
      return true;
  }
  protected function fetch($sql,$param=array()){
    $this->getdb();
    $tmp = self::$cennct->prepare($sql);
    $tmp->execute($param);
    return $tmp->fetch(PDO::FETCH_ASSOC);
  }
  protected function fetchAll($sql,$param=array()){
    $this->getdb();
    $tmp = self::$cennct->prepare($sql);
    $tmp->execute($param);
    return $tmp->fetchAll(PDO::FETCH_ASSOC);     
  }
  protected function execute($sql,$param=array()){
    $this->getdb(); 
    $tmp = self::$cennct->prepare($sql);
    return $tmp->execute($param);
  }
}

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The above is a database operation singleton mode

Singleton mode of php static variables and database classes

The maximum scope of variables (non-Session) in PHP is one request, and static variables will be re-initialized for each request.

Why use PHP singleton mode and application examples

The singleton mode, as its name suggests, means that there is only one instance. As an object creation mode, the singleton mode ensures that a certain class has only one instance, and it instantiates itself and provides this instance to the entire system. This class is called a singleton class. There are three main points of the singleton pattern: first, a class can only have one instance; second, it must create this instance by itself; third, it must provide this instance to the entire system by itself. Let’s discuss why we should use PHP singleton mode? Most people understand the purpose of the singleton pattern from the literal meaning, thinking that it saves system resources, avoids repeated instantiation, and is a kind of "family planning". However, PHP executes the page every time it is executed. All resources will be cleared from memory. Therefore, the singleton in PHP actually needs to be re-instantiated every time it is run, thus losing the meaning of repeated instantiation of the singleton. From this aspect alone, PHP The singleton is indeed a bit disappointing to everyone. But does the singleton only have this function and application? The answer is no, let's take a look. 1. PHP is mainly used in database applications, so there will be a large number of database operations in an application. When developing in an object-oriented way (nonsense), if you use the singleton mode, you can avoid a large number of resources consumed by new operations. 2. If a class is needed in the system to globally control certain configuration information, it can be easily implemented using the singleton mode. For this, please refer to the FrontController part of the zend Framework. 3. In a page request, it is easy to debug because all the code (such as database operation class db) is concentrated in one class. We can set hooks in the class and output logs to avoid var_dump and echo everywhere.