php d what does it mean

php d refers to the D method in Thinkphp, which is used to instantiate a custom model. It is an encapsulation of the Model class instantiation by the ThinkPHP framework, and implements the singleton mode, supporting cross-project and Grouped calls, the calling format is such as "$User = D('User');".

The operating environment of this tutorial: windows7 system, thinkphp v6 version, Dell G3 computer.

php d What does it mean?

About the meaning and usage of D in the Thinkphp framework

D method

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

D('[项目://][分组/]模型','模型层名称')

Return of the method Values ​​are instantiated model objects.

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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