An entry-level Class article

I just browsed the article about Class updated on the homepage (referring to the http://www.phpe.net/articles/389.shtml of PHPE), very good, it is recommended to have a look.
Exploration of classes ~~ It took me half a year to understand the role and implementation of the class. There is not an article that can help me understand (I have never touched any OO stuff before ).
In my opinion, the Class used in PHP is an informal language and cannot be determined whether it is correct.
It is easy to create a class.
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Class my_class {}
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What is the class? Many people use black boxes. Here I refer to them as an independent whole. We only know the class name, but do not know what is in it. So how should we use this class?
First, you need to know whether the public variable is defined in it-technically, it is called "attribute ".
Second, you need to know what function is defined in it-in professional terms, it is called "method ".
I am confused by these technical terms, so I simply ignore it.
How does one define public variables in a class?
It's easy. Let's expand the my_class class.
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Class my_class
{
Var $ username;
}
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The above is simple. We have defined a public variable, which is composed of var + space + common variable names. What is its use? In the function, if we want to access variables outside the function, do we need to make a global operation first? The same is true for this purpose. It is used to allow all functions in this class to access it, and it is different from the function, and the variable can be accessed outside the class, I will talk about how to access it externally. Another difference is that you cannot assign values to this variable using complex statements (you can read the rules yourself after understanding the class ). Give it a default value
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Class my_class
{
Var $ username = "deep space ";
}
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OK, defines a public variable, and then defines a function (that is, the so-called "method ").
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