Protected and const attributes of php classes and objects

This article introduces the use of protected and const attributes of classes and objects in php. For more information, see.

Const attributes
The field defined with the const attribute is a constant. constants in the class are similar to static variables. The difference is that the value of a constant cannot be changed once it is assigned a value.

The const definition constant does not require the $ symbol. Its structure is as follows:

Const constant name // constant name cannot use the $ symbol

Instance:

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<? Php Class Date { Const M = "Monday "; } Echo "today is". Date: M; ?>

Tip: the constant names defined by const are generally capitalized. This is a Convention. We need to develop a good naming convention. If the defined constant is composed of multiple words, the underscore _ link is used, which is also a convention. For example, FILE_SIZE.

Protected attributes

The field scope defined by protected is between public and private. If this member is declared as protected (protected), it means that this field can only be used in this class and its subclass.

Instance:

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<? Php Class me { Protected $ Money = 100; Protected $ price1 = 60;   Public function compute ($ price ){ If ($ this-> price1 <= $ price ){ Echo "okay, I sold it to you. <Br> "; $ This-> Money = $ this-> Money + $ price; Return "I have a total of". $ this-> Money. "RMB "; } Else { Echo "I don't sell it, $ price is too cheap <br> "; Return "Now I am still". $ this-> Money. "RMB "; } } }   $ Now = new me; Echo $ now-> timeout (30 ); ?>