thinkphp what is big d

Big d in thinkphp is a built-in method used to instantiate a custom model class. It is an encapsulation of the Model class instantiation by the ThinkPHP framework. The calling format of the D method is "D('[project ://][Group/]Model','Model layer name')".

The operating environment of this article: Windows 7 system, ThinkPHP version 5.0, Dell G3 computer.

Detailed explanation of ThinkPHP functions: D method

D method:

D method should be used more often method, used to instantiate custom model classes, is an encapsulation of the Model class instantiation by the ThinkPHP framework, and implements the singleton mode, supporting cross-project and group calls. The calling format is as follows:

D('[项目://][分组/]模型','模型层名称')

The return value of the method is the instantiated model object.

D method can automatically detect the model class. If a custom model class exists, the custom model class will be instantiated. If it does not exist, the Model base class will be instantiated. At the same time, for the already instantiated model , will not be instantiated repeatedly. The most common usage of the

D method is to instantiate a custom model of the current project. For example:

// 实例化User模型
$User = D('User');

will import the Lib/Model/UserModel.class.php file under the current project, Then instantiate the UserModel class, so the actual code may be equivalent to the following:

import('@.Model.UserModel');
$User = new UserModel();

But if you use the D method, if the UserModel class does not exist, it will automatically call

new Model('User');

And there is no need to instantiate again when calling for the second time, which can reduce a certain amount of object instantiation overhead.

D method can support cross-group and project instantiation models, for example:

//实例化Admin项目的User模型
D('Admin://User')
//实例化Admin分组的User模型
D('Admin/User')

Note: To implement cross-project calling models, you must ensure that the directory structures of the two projects are parallel.

Starting from version 3.1, due to the added support for hierarchical models, the D method can also instantiate other models, for example:

// 实例化UserService类
$User = D('User','Service');
// 实例化UserLogic类
$User = D('User','Logic');

D('User','Service');

will import Lib/Service/UserService.class.php , and instantiated, equivalent to the following code:

import('@.Service.UserService');
$User = new UserSerivce();

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