Php trait static method

A (somewhat) practical example of trait usage.

class Controller /* Controller-specific methods defined here. */
>

class AdminController extends Controller /* Controller-specific methods inherited from Controller. */
/* Admin-specific methods defined here. */
>

class CrudController extends Controller /* Controller-specific methods inherited from Controller. */
/* CRUD-specific methods defined here. */
>

class AdminCrudController extends CrudController /* Controller-specific methods inherited from Controller. */
/* CRUD-specific methods inherited from CrudController. */
/* (. ) Admin-specific methods copied and pasted from AdminController. */
>

class Controller /* Controller-specific methods defined here. */
>

class AdminController extends Controller /* Controller-specific methods inherited from Controller. */
/* Admin-specific methods defined here. */
>

trait CrudControllerTrait /* CRUD-specific methods defined here. */
>

class AdminCrudController extends AdminController use CrudControllerTrait ;
/* Controller-specific methods inherited from Controller. */
/* Admin-specific methods inherited from AdminController. */
/* CRUD-specific methods defined by CrudControllerTrait. */
>

Adding to «atorich at gmail dot com»:

The behavior of the magic constant __CLASS__ when used in traits is as expected if you understand traits and late static binding (http://php.net/manual/en/language.oop5.late-static-bindings.php).

$format = ‘Class: %-13s | get_class(): %-13s | get_called_class(): %-13s%s’ ;

trait TestTrait public function testMethod () global $format ;
printf ( $format , __CLASS__ , get_class (), get_called_class (), PHP_EOL );
>

public static function testStatic () global $format ;
printf ( $format , __CLASS__ , get_class (), get_called_class (), PHP_EOL );
>
>

trait DuplicateTrait public function duplMethod () global $format ;
printf ( $format , __CLASS__ , get_class (), get_called_class (), PHP_EOL );
>

public static function duplStatic () global $format ;
printf ( $format , __CLASS__ , get_class (), get_called_class (), PHP_EOL );
>
>

abstract class AbstractClass

public function absMethod () global $format ;
printf ( $format , __CLASS__ , get_class (), get_called_class (), PHP_EOL );
>

public static function absStatic () global $format ;
printf ( $format , __CLASS__ , get_class (), get_called_class (), PHP_EOL );
>
>

class BaseClass extends AbstractClass use TestTrait ;
>

class TestClass extends BaseClass

$t -> testMethod ();
TestClass :: testStatic ();

$t -> absMethod ();
TestClass :: absStatic ();

$t -> duplMethod ();
TestClass :: duplStatic ();

Since Traits are considered literal «copying/pasting» of code, it’s clear how the methods defined in DuplicateTrait give the same results as the methods defined in AbstractClass.

Traits are useful for strategies, when you want the same data to be handled (filtered, sorted, etc) differently.

For example, you have a list of products that you want to filter out based on some criteria (brands, specs, whatever), or sorted by different means (price, label, whatever). You can create a sorting trait that contains different functions for different sorting types (numeric, string, date, etc). You can then use this trait not only in your product class (as given in the example), but also in other classes that need similar strategies (to apply a numeric sort to some data, etc).

trait SortStrategy private $sort_field = null ;
private function string_asc ( $item1 , $item2 ) return strnatcmp ( $item1 [ $this -> sort_field ], $item2 [ $this -> sort_field ]);
>
private function string_desc ( $item1 , $item2 ) return strnatcmp ( $item2 [ $this -> sort_field ], $item1 [ $this -> sort_field ]);
>
private function num_asc ( $item1 , $item2 ) if ( $item1 [ $this -> sort_field ] == $item2 [ $this -> sort_field ]) return 0 ;
return ( $item1 [ $this -> sort_field ] < $item2 [ $this ->sort_field ] ? — 1 : 1 );
>
private function num_desc ( $item1 , $item2 ) if ( $item1 [ $this -> sort_field ] == $item2 [ $this -> sort_field ]) return 0 ;
return ( $item1 [ $this -> sort_field ] > $item2 [ $this -> sort_field ] ? — 1 : 1 );
>
private function date_asc ( $item1 , $item2 ) $date1 = intval ( str_replace ( ‘-‘ , » , $item1 [ $this -> sort_field ]));
$date2 = intval ( str_replace ( ‘-‘ , » , $item2 [ $this -> sort_field ]));
if ( $date1 == $date2 ) return 0 ;
return ( $date1 < $date2 ? - 1 : 1 );
>
private function date_desc ( $item1 , $item2 ) $date1 = intval ( str_replace ( ‘-‘ , » , $item1 [ $this -> sort_field ]));
$date2 = intval ( str_replace ( ‘-‘ , » , $item2 [ $this -> sort_field ]));
if ( $date1 == $date2 ) return 0 ;
return ( $date1 > $date2 ? — 1 : 1 );
>
>

class Product public $data = array();

public function get () // do something to get the data, for this ex. I just included an array
$this -> data = array(
101222 => array( ‘label’ => ‘Awesome product’ , ‘price’ => 10.50 , ‘date_added’ => ‘2012-02-01’ ),
101232 => array( ‘label’ => ‘Not so awesome product’ , ‘price’ => 5.20 , ‘date_added’ => ‘2012-03-20’ ),
101241 => array( ‘label’ => ‘Pretty neat product’ , ‘price’ => 9.65 , ‘date_added’ => ‘2012-04-15’ ),
101256 => array( ‘label’ => ‘Freakishly cool product’ , ‘price’ => 12.55 , ‘date_added’ => ‘2012-01-11’ ),
101219 => array( ‘label’ => ‘Meh product’ , ‘price’ => 3.69 , ‘date_added’ => ‘2012-06-11’ ),
);
>

public function sort_by ( $by = ‘price’ , $type = ‘asc’ ) if (! preg_match ( ‘/^(asc|desc)$/’ , $type )) $type = ‘asc’ ;
switch ( $by ) case ‘name’ :
$this -> sort_field = ‘label’ ;
uasort ( $this -> data , array( ‘Product’ , ‘string_’ . $type ));
break;
case ‘date’ :
$this -> sort_field = ‘date_added’ ;
uasort ( $this -> data , array( ‘Product’ , ‘date_’ . $type ));
break;
default:
$this -> sort_field = ‘price’ ;
uasort ( $this -> data , array( ‘Product’ , ‘num_’ . $type ));
>
>
>

$product = new Product ();
$product -> get ();
$product -> sort_by ( ‘name’ );
echo ‘

' . print_r ( $product -> data , true ). '

‘ ;
?>

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