The concepts and differences between PHP abstract classes and interfaces

//1. Define some methods, and the subclass must fully implement all methods in this abstraction
//2. Objects cannot be created from abstract classes. The meaning of this is Being extended
//3. Abstract classes usually have abstract methods, and there are no braces in the methods
//4. Abstract methods do not have to implement specific functions, and are completed by subclasses
//5. Implement methods of abstract classes in subclasses When, the visibility of its subclass must be greater than or equal to the definition of the abstract method
//6. The method of the abstract class can have parameters or be empty
//7. If the abstract method has parameters, then the implementation of the subclass also Must have the same number of parameters
///////////////////////////////Interface class Definition:
interface Shop{
 public function buy($gid);
 public function sell($gid);
 abstract function view($gid);
}
//If you want to use the interface, you must define all the parameters in the interface class No method can be missing (except abstract).
//In this way, if in a large project, no matter how others do the following method, they must implement all the methods in this interface!

//Example: Implement the above A method of the interface
class BaseShop implements Shop{
 public function buy($gid){
 echo 'You purchased the product with the ID:' . $gid . '';
 }
 public function sell($gid){
 echo 'You purchased and sold products with ID:' . $gid . '';
 }
 public function view($gid){
 echo 'You browsed products with ID:' . $gid . '';
 }
}
//Example of multiple inheritance of interface:

interface staff_i1{ //Interface 1
 function setID();
 function getID();
}
interface staff_i2{ //Interface 2
 function setName();
 function getName();
}
class staff implements staff_i1,staff_i2{
 private $id ;
 private $name;
 function setID($id){
 $this->id = $id;
 }
 function getID(){
 return $this->id ;
 }
 function setName($name){
 $this->name = $name;
 }
 function getName(){
 return $this->name;
 }
 function otherFunc(){ //This is a method that does not exist in the interface
 echo “Test”;
 }
}
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