Using factory pattern in PHP

A factory class refers to a class that contains a method specifically used to create other objects. The factory class is crucial in the practice of polymorphic programming. It allows dynamic replacement of classes and modification of configurations, which generally makes the application more flexible. , it is important for senior PHP developers to be proficient in factory mode.

The factory pattern is usually used to return different classes that conform to similar interfaces. A common use of factories is to create polymorphic providers, allowing us to decide which class should be instantiated based on application logic or configuration settings, such as , you can use such a provider to extend a class without having to refactor other parts of the application to use the new extended name.

Usually, the factory pattern has a key construct, which is a static method named Factory according to general principles. However, this is just a principle. The factory method can be named arbitrarily. This static method can also accept parameters of any data and must return an object.

Basic factory class

class MyObject{  
  //对象将从工厂返回  
}  
  
class MyFactory{  
public static function factory(){  
return new MyObject():  
   }  
}  
  
$instance=MyFactory::factory();

Use factory class to parse image files

Php code

<?php  
interface IImage{  
    function getHeight();  
    function getWidth();  
    function getData();  
}  
  
class Image_PNG implements IImage{  
      
    private $_width,$_height,$_data;  
      
    public function __construct($file){  
        $this->_file=$file;  
        $this->_parse();  
    }  
          
    private function _parse(){  
              
            //完成PNG格式的解析工作  
            //并填充$_width,$_height,$_data;  
        }  
          
          
    public function getWidth(){  
        return $this->_width;  
    }  
    public  function getHeight(){  
        return $this->_height;  
    }  
      
    public function getData(){  
       return $this->_data;  
      
    }  
      
}  
  
class Image_JPEG implements IImage{  
      
    private $_width,$_height,$_data;  
      
    public function __construct($file){  
        $this->_file=$file;  
        $this->_parse();  
    }  
          
    private function _parse(){  
              
            //完成JPEG格式的解析工作  
            //并填充$_width,$_height,$_data;  
        }  
          
          
    public function getWidth(){  
        return $this->_width;  
    }  
    public  function getHeight(){  
        return $this->_height;  
    }  
      
    public function getData(){  
       return $this->_data;  
      
    }  
      
}  
  
class ImageFactory{  
      
    public static function factory($file){  
        $pathParts=pathinfo($file);  
        switch (strtolower($pathParts[&#39;extension&#39;]))  
        {  
            case &#39;jpg&#39;:  
                $ret=new Image_JPEG($file);  
                break;  
            case &#39;png&#39;:  
                $ret=new Image_PNG($file);  
                break;  
                default:  
                    //有问题  
  
                      
        }  
        if($ret instanceof IImage){  
            return $ret;  
        }else {  
            //有问题  
        }  
    }  
}  
  
//当使用图像文件名调用 工厂方法时，根据传入的文件类型不同，取得不同对象。

Php code

//调用ImageFactoyr  
$image=ImageFactory::factory('/path/to/my.jpg');  
//$image是Image_JPEG类的一个实例  
echo $image->getWidth();

Use factory class to solve the problem of database portability. In database applications, the factory pattern can be used in the following two works in all aspects.

1. Make it easier for the software to support various database platforms to expand the user base

2. If the software is used internally and the database needs to be modified, the application can be easily migrated to another platform

In the code, a database table named User is created to test it. This table defines a varchar type field named email

Php code

<?php  
interface IDatabaseBindings{  
    public function userExists($email);  
}  
  
class PGSQL implements IDatabaseBindings{  
    protected $_connection;  
      
    public function __construct(){  
          
        $this->_connection=pg_connect(&#39;dbname=example_db&#39;);  
    }  
      
    public function userExists($email){  
          
        $emailEscaped=pg_escape_string($email);  
        $query="select 1 from users where email=&#39;".$emailEscaped."&#39;";  
        if($result=pg_query($query,$this->_connection)){  
            return (pg_num_rows($result)>0)?true:false;  
        }else{  
            return false;  
        }  
    }  
      
}  
  
class MYSQL implements IDatabaseBindings{  
      
    protected $_connection;  
      
    public function __construct(){  
          
        $this->_connection=mysql_connect(&#39;localhost&#39;);  
        mysql_select_db(&#39;example_db&#39;,$this->_connection);  
    }  
      
    public function userExists($email){  
          
        $emailEscaped=mysql_real_escape_string($email);  
        $query="select 1 from users where email=&#39;".$emailEscaped."&#39;";  
        if($result=mysql_query($query,$this->_connection)){  
            return (mysql_num_rows($result)>0)?true:false;  
        }else{  
            return false;  
        }  
    }  
      
}  
  
class DatabaseFactory{  
      
    public static function factory(){  
        $type=loadtypefromconfigfile();  
        switch ($type){  
            case &#39;PGSQL&#39;:  
                return new PGSQL();  
                break;  
            case &#39;MYSQL&#39;:  
                return new MYSQL();  
                break;  
        }  
    }  
}

The application does not have to know what type of database it is connected to , will only directly deal with the instances returned by the factory based on the rules defined by the IDatabaseBindings interface.

Php code

//调用DatabaseFactoy  
$db=DatabaseFactory::factory();  
$db->userExists('person@example.com');

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