Php object-oriented? Static Member

Php object-oriented? Static Member Php object-oriented? Static Member

Static attributes

Attributes declared using the static keyword

This static property is logically defined in the class. Ensure that a class corresponds to an attribute.

Example:

Class Student

{

Public $ stu_id;

Public $ stu_name;

Public static $ stu_count = 0;

Public function _ constuct ($ id, $ name)

{

$ This-> stu_id = $ id;

$ This-> stu_name = $ name;

}
}

Access static attributes:

Access through the class: in the use of static access symbols (::)

Class: Member

Example:

Class Student

{

Public $ stu_id;

Public $ stu_name;

Public static $ stu_count = 0;

Public function _ constuct ($ id, $ name)

{

$ This-> stu_id = $ id;

$ This-> stu_name = $ name;

Student: $ stu_count ++;

}
}

: The access is called static access.-> Non-static access (object access)

When you access static attributes, if you access them within the class: you can use the current class of self.

Example:

Class Student

{

Public $ stu_id;

Public $ stu_name;

Public static $ stu_count = 0;

Public function _ constuct ($ id, $ name)

{

$ This-> stu_id = $ id;

$ This-> stu_name = $ name;

Self: $ stu_count ++;

}
}

Note: the difference between $ this and self

$ This indicates this object, and self indicates this class.

Static method

The logic meaning of static methods is also a method that defines the class. Similarly, the call form class ::

Example:

Class Student

{

Public $ stu_id;

Public $ stu_name;

Public static $ stu_count = 0;

Public function _ constuct ($ id, $ name)

{

$ This-> stu_id = $ id;

$ This-> stu_name = $ name;

Self: $ stu_count ++;

}

Public static function sayCount ()

{

Echo "run static ";

}
}

Student: sayCount ();

The main difference between static and non-static methods is whether an object's execution environment can be received.

Is it possible to assign a value to $ this in the method?

Only when an object calls a method can the object execution environment be passed to the method, and $ this can be assigned a value.

Non-static attributes cannot be used in static methods.

One static method can only process static data (static attributes)

Example:

Class Student

{

Public $ stu_id;

Public $ stu_name;

Public static $ stu_count = 0;

Public function _ constuct ($ id, $ name)

{

$ This-> stu_id = $ id;

$ This-> stu_name = $ name;

Self: $ stu_count ++;

}

Public static function sayCount ()

{

Echo self: $ stu_count;

}
}

Student: sayCount ();

Special method access problems in Php:

Emphasis: static methods should be called by class, non-static methods should be called by objects

Class C

{

Public function f1 ()

{

Echo 'F1
';

}

Public static function f2 ()

{

Echo 'F2
';

}

}

$ O = new C;

$ O-> f1 ();

C: f2 ();

However:

1. both static and non-static methods can be accessed using classes: However, if a class calls a non-static method statically, an error with nonstandard syntax is reported.

2. The difference lies in $ this.

You can use $ this in the method only when you call a non-static method using an object.

Class C

{

Public function f1 ()

{

Echo 'F1
';

}

Public static function f2 ()

{

Echo 'F2
';

}

}

C: f1 ();

C: f2 ();

Summary: the static and non-static methods of the class are saved in only one copy, but the runtime environment is different. You can use $ this in the method only when you call a non-static method using an object.