Главная » Языки программирования

Php object all attributes

Содержание
  1. get_object_vars
  2. Parameters
  3. Return Values
  4. Examples
  5. See Also
  6. User Contributed Notes 5 notes
  7. Php object all attributes

get_object_vars

Gets the accessible non-static properties of the given object according to scope.

Parameters

Return Values

Returns an associative array of defined object accessible non-static properties for the specified object in scope.

Examples

Example #1 Use of get_object_vars()

class foo private $a ;
public $b = 1 ;
public $c ;
private $d ;
static $e ;

public function test () var_dump ( get_object_vars ( $this ));
>
>

$test = new foo ;
var_dump ( get_object_vars ( $test ));

The above example will output:

array(2) < ["b"]=>int(1) ["c"]=> NULL > array(4) < ["a"]=>NULL ["b"]=> int(1) ["c"]=> NULL ["d"]=> NULL >

Note:

Uninitialized properties are considered inaccessible, and thus will not be included in the array.

See Also

User Contributed Notes 5 notes

You can still cast the object to an array to get all its members and see its visibility. Example:

class Potatoe public $skin ;
protected $meat ;
private $roots ;

function __construct ( $s , $m , $r ) $this -> skin = $s ;
$this -> meat = $m ;
$this -> roots = $r ;
>
>

$Obj = new Potatoe ( 1 , 2 , 3 );

echo «\n» ;
echo «Using get_object_vars:\n» ;

$vars = get_object_vars ( $Obj );
print_r ( $vars );

$Arr = (array) $Obj ;
print_r ( $Arr );

Using get_object_vars:
Array
(
[skin] => 1
)

Using array cast:
Array
(
[skin] => 1
[ * meat] => 2
[ Potatoe roots] => 3
)

As you can see, you can obtain the visibility for each member from this cast. That which seems to be spaces into array keys are ‘\0’ characters, so the general rule to parse keys seems to be:

Public members: member_name
Protected memebers: \0*\0member_name
Private members: \0Class_name\0member_name

I’ve wroten a obj2array function that creates entries without visibility for each key, so you can handle them into the array as it were within the object:

function obj2array ( & $Instance ) $clone = (array) $Instance ;
$rtn = array ();
$rtn [ ‘___SOURCE_KEYS_’ ] = $clone ;

while ( list ( $key , $value ) = each ( $clone ) ) $aux = explode ( «\0» , $key );
$newkey = $aux [ count ( $aux )- 1 ];
$rtn [ $newkey ] = & $rtn [ ‘___SOURCE_KEYS_’ ][ $key ];
>

?>

I’ve created also a bless function that works similar to Perl’s bless, so you can further recast the array converting it in an object of an specific class:

// First get source keys if available
if ( isset ( $Instance [ ‘___SOURCE_KEYS_’ ])) $Instance = $Instance [ ‘___SOURCE_KEYS_’ ];
>

// Get serialization data from array
$serdata = serialize ( $Instance );

list ( $array_params , $array_elems ) = explode ( ‘ list ( $array_tag , $array_count ) = explode ( ‘:’ , $array_params , 3 );
$serdata = «O:» . strlen ( $Class ). «:\» $Class \»: $array_count :

$Instance = unserialize ( $serdata );
return $Instance ;
>
?>

With these ones you can do things like:

define ( «SFCMS_DIR» , dirname ( __FILE__ ). «/..» );
require_once ( SFCMS_DIR . «/Misc/bless.php» );

class Potatoe public $skin ;
protected $meat ;
private $roots ;

function __construct ( $s , $m , $r ) $this -> skin = $s ;
$this -> meat = $m ;
$this -> roots = $r ;
>

function PrintAll () echo «skin keyword»>. $this -> skin . «\n» ;
echo «meat keyword»>. $this -> meat . «\n» ;
echo «roots keyword»>. $this -> roots . «\n» ;
>
>

$Obj = new Potatoe ( 1 , 2 , 3 );

echo «\n» ;
echo «Using get_object_vars:\n» ;

$vars = get_object_vars ( $Obj );
print_r ( $vars );

echo «\n\nUsing obj2array func:\n» ;

$Arr = obj2array ( $Obj );
print_r ( $Arr );

echo «\n\nSetting all members to 0.\n» ;
$Arr [ ‘skin’ ]= 0 ;
$Arr [ ‘meat’ ]= 0 ;
$Arr [ ‘roots’ ]= 0 ;

echo «Converting the array into an instance of the original class.\n» ;
bless ( $Arr , Potatoe );

if ( is_object ( $Arr ) ) echo «\$Arr is now an object.\n» ;
if ( $Arr instanceof Potatoe ) echo «\$Arr is an instance of Potatoe class.\n» ;
>
>

Please be aware of hidden behaviors with uninitialised properties. The note explains : « Uninitialized properties are considered inaccessible, and thus will not be included in the array. » but that’s not entirely true in PHP 8.1. It depends if the property is type-hinted or not.

class Example
public $untyped ;
public string $typedButNotInitialized ;
public ? string $typedOrNullNotInitialized ;
public ? string $typedOrNullWithDefaultNull = null ;
>

var_dump ( get_object_vars (new Example ()));
?>

will print :

array(2) [«untyped»]=>
NULL
[«typedOrNullWithDefaultNull»]=>
NULL
>

As you can see, only «untyped» and «typedOrNullWithDefaultNull» properties are dumped with get_object_vars(). You may encounter problems when migrating old source code and adds carelessly types everywhere without proper initialisation (or default) and assuming it defaults to NULL like old code does.

You can use an anonymous class to return public variables from inside the class:

public function getPublicVars () $me = new class function getPublicVars($object) return get_object_vars($object);
>
>;
return $me->getPublicVars($this);
>

class Test protected $protected;
public $public;
private $private;
public function getAllVars () return call_user_func(‘get_object_vars’, $this);
>
public function getPublicVars () $me = new class function getPublicVars($object) return get_object_vars($object);
>
>;
return $me->getPublicVars($this);
>
>

$test = new Test();
print_r(get_object_vars($test)); // array(«public» => NULL)
print_r($test->getAllVars()); // array(«protected» => NULL, «public» => NULL, «private» => NULL)
print_r($test->getPublicVars()); // array(«public» => NULL)

When dealing with a very large quantity of objects, it is worth noting that using `get_object_vars()` may drastically increase memory usage.

If instantiated objects only use predefined properties from a class then PHP can use a single hashtable for the class properties, and small memory-efficient arrays for the object properties:

If a class is defined with three properties ($foo, $bar, and $baz), «PHP no longer has to store the data in a hashtable, but instead can say that $foo is proprety 0, $bar is proprety 1, $baz is property 2 and then just store the properties in a three-element C array. This means that PHP only needs one hashtable in the class that does the property-name to offset mapping and uses a memory-efficient C-array in the individual objects.»

However, if you call `get_object_vars()` on an object like this, then PHP WILL build a hashtable for the individual object. If you have a large quantity of objects, and you call `get_object_vars()` on all of them, then a hashtable will be built for each object, resulting in a lot more memory usage. This can be seen in this bug report: https://bugs.php.net/bug.php?id=79392

The effects of this can be seen in this example:

class Example public $foo ;
public $bar ;
public $baz ;
>

function printMem ( $label ) $usage = memory_get_usage ();
echo sprintf ( ‘%s: %d (%.2f MB)’ , $label , $usage , $usage / 1000000 ) . PHP_EOL ;
>

$objects = [];
for ( $i = 0 ; $i < 20000 ; $i ++) $obj = new Example ;
$obj -> foo = bin2hex ( random_bytes ( 5 ));
$obj -> bar = bin2hex ( random_bytes ( 5 ));
$obj -> baz = bin2hex ( random_bytes ( 5 ));
$objects [] = $obj ;
>

printMem ( ‘before get_object_vars’ );

// Clone each object, and get the vars on the clone
foreach ( $objects as $obj ) $c = clone $obj ;
$vars = get_object_vars ( $c );

// Accessing and modifying the original object is fine.
foreach ( $vars as $var => $val ) $obj -> < $var >= strrev ( $val );
>
>

printMem ( ‘get_object_vars using clone’ );

// Get the vars on each object directly
foreach ( $objects as $obj ) $vars = get_object_vars ( $obj );

// The memory is used even if you do not modify the object.
>

printMem ( ‘get_object_vars direct access’ );
?>

The output of this is:

start: 405704 (0.41 MB)
before get_object_vars: 6512416 (6.51 MB)
get_object_vars using clone: 6033408 (6.03 MB)
get_object_vars direct access: 13553408 (13.55 MB)

In short, if you are using classes to avoid additional memory usage associated with hashtables (like in associative arrays), be aware that `get_object_vars()` will create a hashtable for any object passed to it.

This appears to be present in all versions of PHP; I’ve tested it on PHP 5, 7, and 8.

Quotes are from Nikic’s blog posts on arrays and hashtable memory usage, and Github gist «Why objects (usually) use less memory than arrays in PHP».

It seems like there’s no function that determines all the *static* variables of a class.

I’ve come out with this one as I needed it in a project:

function get_class_static_vars ( $object ) <
return array_diff ( get_class_vars ( get_class ( $object )), get_object_vars ( $object ));
>
?>

It relies on an interesting property: the fact that get_object_vars only returns the non-static variables of an object.

Оцените статью
© 2024 Программирование