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What is Interfaces

 

In PHP, interfaces serve a similar purpose as in other programming languages: they define a contract that classes must adhere to. PHP interfaces specify a set of method signatures that classes implementing the interface must define. However, unlike some other languages, PHP interfaces cannot contain method implementations, only method signatures.

 

Here are the key aspects of PHP interfaces:

 

Declaration

 

  • Interfaces are declared using the interface keyword followed by the interface name.
  • Inside the interface, only method signatures (including their visibility modifiers) and constants can be defined. Method implementations are not allowed.

 

Implementation

 

  • A class implements an interface using the implements keyword followed by the interface name.
  • Any class that implements an interface must define all the methods declared in the interface.

 

Multiple Interfaces

 

  • A class can implement multiple interfaces by separating interface names with commas.

 

​​​​​​​Usage

 

  • Interfaces are commonly used to define a common set of methods that classes of different types can implement. This promotes code reusability and abstraction.

 

​​​​​​​Example

 

 

// Define an interface
interface Printable {
    public function printDocument();
}

// Implement the interface in a class
class Document implements Printable {
    public function printDocument() {
        echo "Printing document...";
    }
}

// Implement the interface in another class
class Invoice implements Printable {
    public function printDocument() {
        echo "Printing invoice...";
    }
}

 

 

 

In this example, the Printable interface defines a single method printDocument(). Both the Document and Invoice classes implement this interface by providing their own implementations of the printDocument() method.

PHP interfaces are commonly used in scenarios where you want to define a contract that multiple classes must adhere to, without enforcing a specific inheritance hierarchy. They are especially useful in situations where you want to provide a common interface for classes that serve different purposes but share common behavior.