Six pre-defined interfaces in PHP

Six pre-defined interfaces in PHP

This article mainly introduces six pre-defined interfaces in PHP. This article describes Traversable, Iterator, IteratorAggregate, ArrayAccess, Serializable, and Closure. For more information, see

PHP predefines six 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.

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If ($ class instanceof Traversable ){ // Foreach }

2. Iterator Interface

Interface Abstract:

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Iterator extends Traversable { // Returns the element pointed to by the current index cursor Abstract public mixed current (void) // Return the key name of the element pointed to by the current index cursor Abstract public scalar key (void) // Move the current index cursor to the next element Abstract public void next (void) // Reset the index cursor pointing to the first element Abstract public void rewind (void) // Determines whether the current index cursor points to an element. It is often used when rewind () or next () is called. Abstract public boolean valid (void) }

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

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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:

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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.

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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:

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ArrayAccess { /* Method */ Abstract public boolean offsetExists (mixed $ offset) // check whether the offset position exists Abstract public mixed offsetGet (mixed $ offset) // gets the value of an offset position. Abstract public void offsetSet (mixed $ offset, mixed $ value) // you can specify a value for an offset. Abstract public void offsetUnset (mixed $ offset) // reset the value of an offset position }

You can access an object like an array as follows:

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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:

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Serializable {   /* Method */ Abstract public string serialize (void) // string representation of an object Abstract public mixed unserialize (string $ serialized) // construct an 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.

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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:

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Closure { /* Method */ _ Construct (void) // constructor used to disable instantiation 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 it to the specified $ this object and Class scope. }

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Class { 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 ";