Php object-oriented-class constants, php object-oriented Constants

Php object-oriented-class constants, php object-oriented Constants

Php object-oriented-class Constants

 

Class constant: in the class, data that remains unchanged during the running period is saved.

Definition:

Const keyword

Const constant name = constant value

 

Example:

 

Class Student

{

Public $ stu_id;

Public $ stu_name;

Public $ stu_gender;

Const GENDER_MALE = 'male ';

Const GENDER_FEMALE = 'femal ';

 

}

 

Class constants are not restricted by access modifiers.

 

 

Access:

Class: constant name

 

Example:

 

Class Student

{

Public $ stu_id;

Public $ stu_name;

Public $ stu_gender;

Const GENDER_MALE = 'male ';

Const GENDER_FEMALE = 'femal ';

 

Public function _ construct ($ id, $ name, $ gender = '')

{

$ This-> stu_id = $ id;

$ This-> stu_name = $ name;

$ This-> gender = ($ gender = '')? Self: GENDER_MALE: $ gender;

}

 

}

 

Summary: Members that can be defined in the class, including constants, static attributes, non-static attributes, static methods, and non-static methods.

 

Note: $ this indicates the current object, always indicates the object of the class where $ this is located?

No, because the value of $ this does not depend on the class where $ this is located, but on the execution object (Execution Environment) when the $ this method is called)

The execution environment of the method, in which the current method is executed

$ This indicates the object.

 

 

 

 

 

 

 

 

How can a php Object obtain a constant outside the class?

Instantiate a class object, and then find the constant you want in the class through the class object. You can also use the class name to find a constant.

Why does php set up class constants?

The benefit of using a class constant is:

-No additional overhead for parsing during compilation
-The pooled tables are smaller, so internal search is faster.
-The class constant only exists in the specified "namespace", so the name of the miscellaneous is shorter.
-Code cleaner to make debugging easier