Which of the following experts can help me explain how to automatically load classes?

Who can help me explain how to automatically load the class/* require (ROOT. 'include/db. class. php '); require (ROOT. 'include/conf. class. php '); require (ROOT. 'include/log. class. php '); require (R, who can help me explain how to automatically load classes?

/*
Require (ROOT. 'include/db. class. php ');
Require (ROOT. 'include/conf. class. php ');
Require (ROOT. 'include/log. class. php ');
Require (ROOT. 'include/mysql. class. php ');
Require (ROOT. 'model/Model. class. php ');
Require (ROOT. 'model/TestModel. class. php ');
*/


Function _ autoload ($ class ){
If (strtolower (substr ($ class,-5) = 'model '){
Require (ROOT. 'model/'. $ class.'. class. php ');
} Else {
Require (ROOT. 'include/'. $ class.'. class. php ');
}
}
The above deregistered is the manual loading class, and the following is the automatic loading

I don't quite understand where the $ class comes from
------ Solution --------------------
When you use new classname
If the classname class does not exist, php will call the _ autoload function and pass the classname
------ Solution --------------------
$ Class is the class name that cannot be found
The automatically loaded class is the class that cannot be automatically loaded.