Six pre-defined interfaces in PHP

This article mainly introduces six pre-defined interfaces in PHP. This article describes Traversable, Iterator, IteratorAggregate, ArrayAccess, Serializable, Closure, you can refer to PHP to describe 6 predefined interfaces as follows:

1. Traversable traversal interface

Haha! In fact, it is not an interface that can be used in PHP, and internal classes can be used. it has a purpose to detect whether a class can be traversed.

if($class instanceof Traversable) {  //foreach}

2. Iterator interface

Interface abstract:

Iterator extends Traversable {// returns the abstract public mixed current (void) element pointed to by the current index cursor // returns the abstract public scalar key (void) key name of the element pointed to by the current index cursor) // Move the current index cursor to the next element abstract public void next (void) // reset the index cursor to the first element abstract public void rewind (void) // Determine whether the current index cursor points to an element. it is often used to call rewind () or next () to use abstract public boolean valid (void )}

The above allows a class to implement a basic iteration function, as shown in the following figure:

class myIterator implements Iterator {  private $position = 0 ;  private $array = array(    "firstelement" ,    "secondelement" ,    "lastelement" ,  );   public function __construct () {    $this -> position = 0 ;  }   function rewind () {    var_dump ( __METHOD__ );    $this -> position = 0 ;  }   function current () {    var_dump ( __METHOD__ );    return $this -> array [ $this -> position ];  }   function key () {    var_dump ( __METHOD__ );    return $this -> position ;  }   function next () {    var_dump ( __METHOD__ );    ++ $this -> position ;  }   function valid () {    var_dump ( __METHOD__ );    return isset( $this -> array [ $this -> position ]);  }} $it = new myIterator ; foreach( $it as $key => $value ) {  var_dump ( $key , $value );  echo "\n" ;}

3. IteratorAggregate aggregate iterator interface

Interface abstract:

IteratorAggregate extends Traversable {// Obtain the external iterator abstract public Traversable getIterator (void )}

GetIterator is an instance of the class of an Iterator or a Traversable interface. Obtain the external iterator for iterative access as follows.

class myData implements IteratorAggregate {  public $property1 = "Public property one" ;  public $property2 = "Public property two" ;  public $property3 = "Public property three" ;   public function __construct () {    $this -> property4 = "last property" ;  }     public function getIterator () {    return new ArrayIterator ( $this );  }} $obj = new myData ; foreach( $obj as $key => $value ) {  var_dump ( $key , $value );  echo "\n" ;}

4. ArrayAccess array access interface

Interface abstract:

ArrayAccess {/* method */abstract public boolean offsetExists (mixed $ offset) // check whether the offset position contains abstract public mixed offsetGet (mixed $ offset) // obtain the value of an offset position abstract public void offsetSet (mixed $ offset, mixed $ value) // set the value of an offset position abstract public void offsetUnset (mixed $ offset) // reset the value at an offset position}

You can access an object like an array as follows:

class obj implements arrayaccess {  private $container = array();  public function __construct () {    $this -> container = array(      "one"  => 1 ,      "two"  => 2 ,      "three" => 3 ,    );  }  public function offsetSet ( $offset , $value ) {    if ( is_null ( $offset )) {      $this -> container [] = $value ;    } else {      $this -> container [ $offset ] = $value ;    }  }  public function offsetExists ( $offset ) {    return isset( $this -> container [ $offset ]);  }  public function offsetUnset ( $offset ) {    unset( $this -> container [ $offset ]);  }  public function offsetGet ( $offset ) {    return isset( $this -> container [ $offset ]) ? $this -> container [ $offset ] : null ;  }} $obj = new obj ; var_dump (isset( $obj [ "two" ]));var_dump ( $obj [ "two" ]);unset( $obj [ "two" ]);var_dump (isset( $obj [ "two" ]));$obj [ "two" ] = "A value" ;var_dump ( $obj [ "two" ]);$obj [] = 'Append 1' ;$obj [] = 'Append 2' ;$obj [] = 'Append 3' ;print_r ( $obj );

5. Serializable serialization interface

Interface abstract:

Serializable {/* method */abstract public string serialize (void) // The string of the object indicates abstract public mixed unserialize (string $ serialized) // Construct object}

Classes implementing this interface no longer support _ sleep () and _ wakeup (). It is easy to use. as long as the serialize method is called during object serialization, the unserialize method is called during deserialization.

class obj implements Serializable {  private $data ;  public function __construct () {    $this -> data = "My private data" ;  }  public function serialize () {    return serialize ( $this -> data );  }  public function unserialize ( $data ) {    $this -> data = unserialize ( $data );  }  public function getData () {    return $this -> data ;  }} $obj = new obj ;$ser = serialize ( $obj );print_r($ser);$newobj = unserialize ( $ser );print_r($newobj);

6. Closure
Interface abstract:

Closure {/* method */_ construct (void) // The public static Closure bind (Closure $ closure, object $ newthis [, mixed $ newscope = 'static ']) // Copy a closure and bind it to the specified $ this object and class scope. Public Closure bindTo (object $ newthis [, mixed $ newscope = 'static ']) // copy the current Closure object and bind the specified $ this object and class scope .}

class A {  private static $sfoo = 1 ;  private $ifoo = 2 ;} $cl1 = static function() {  return A :: $sfoo ;}; $cl2 = function() {  return $this -> ifoo ;};  $bcl1 = Closure :: bind ( $cl1 , null , 'A' ); $bcl2 = Closure :: bind ( $cl2 , new A (), 'A' );echo $bcl1 (), "\n" ;echo $bcl2 (), "\n" ;