What is the difference between d() and m() in ThinkPHP

Difference: The M method is used to efficiently instantiate a basic model class; while the D method is used to instantiate a user-defined model class. The M method does not need to create a model class file, and the M method does not read the model class; while the D method must create a model class.

#The operating environment of this tutorial: Windows 7 system, thinkphp version 6, Dell G3 computer.

The difference between M method and D method

• In ThinkPHP, both M method and D method are used to instantiate a model class, and M method is used is used to efficiently instantiate a base model class, while the D method is used to instantiate a user-defined model class.

• The M method does not need to create a model class file. The M method does not read the model class, so automatic verification is invalid by default, but it can be achieved through dynamic assignment; and The D method must create a model class.

Use M method

If the following situation occurs, please consider using the M method:

• When performing simple CURD operations on the data table without complex business logic

• When only a few tables have relatively complex business logic, use the M method in combination with the instantiated CommonModel class.

The M method can even simply look at the data corresponding to the parameter table name. Table operations:

$User = M('User');

Use D method

If the following situation occurs, please consider using method D:

• You need to use some advanced functions in the ThinkPHP model such as automatic verification function (implemented in the create() method), associated models, etc.

• The business logic is relatively complex and involves many tables

• The business logic is defined in a custom model class (under the Lib/Model directory) , and want to implement these business logic in the operation

In addition, D method does not support cross-project calls and needs to be used:

$User = D('User', 'Admin');    // 实例化 Admin 项目下面的 User 模型 
$User = D('Admin.User');        // 启用了项目分组

Tips

After project grouping is enabled, the Model class does not necessarily correspond to the project grouping. Model classes shared among multiple project groups are placed in the Model directory and can be instantiated directly using D('ModelName'). And D('User.UserInfo') does not mean that User must be a project group, or it can just be a classification directory of files under Model. D('User.UserInfo') instantiates the UserInfo model in the User directory. kind.

Summarize

Both the M method and the D method can be used directly when the model class file does not exist, but obviously the M method is more efficient; but to use the business logic in the model class, you must use the D method.

A more vivid metaphor is: Method M is like a computer that has just installed the operating system and can only use some basic functions; Method D is like installing some application software such as Office and QQ on the installed system. The functions are more powerful, and at the same time the entire computer runs slower.

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