property_exists

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

property_exists — Prüft auf die Existenz einer Eigenschaft eines Objektes bzw. einer Klasse

Beschreibung

property_exists(object|string $object_or_class, string $property): bool

Prüft ob die Eigenschaft property in der angegebenen Klasse existiert.

Hinweis:
Anders als isset() gibt property_exists() auch dann true zurück, wenn eine Eigenschaft den Wert null hat.

Parameter-Liste

object_or_class: Objektexemplar oder Name der Klasse.
property: Name der zu prüfenden Eigenschaft.

Rückgabewerte

Gibt true zurück, wenn die Eigenschaft existiert, false wenn nicht, und null im Fehlerfall.

Beispiele

Beispiel #1 Ein property_exists() Beispiel

<?php

class myClass {
    public $mine;
    private $xpto;
    static protected $test;

    static function test() {
        var_dump(property_exists('myClass', 'xpto')); //true
    }
}

var_dump(property_exists('myClass', 'mine'));   //true
var_dump(property_exists(new myClass, 'mine')); //true
var_dump(property_exists('myClass', 'xpto'));   //true
var_dump(property_exists('myClass', 'bar'));    //false
var_dump(property_exists('myClass', 'test'));   //true
myClass::test();

?>

Anmerkungen

Hinweis:
Ein Aufruf dieser Funktion verwendet alle registrierten Autoloader, falls die Klasse nicht bereits bekannt ist.

Hinweis:
Die property_exists() Funktion kann keine Eigenschaften erkennen die über die 'magische' Methode __get implementiert sind.

Siehe auch

method_exists() - Prüft ob eine Methode innerhalb eines Objekts existiert

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User Contributed Notes 10 notes

down

g dot gentile at parentesigraffe dot com ¶

9 years ago

The function behaves differently depending on whether the property has been present in the class declaration, or has been added dynamically, if the variable has been unset()

<?php

class TestClass {

    public $declared = null;
    
}

$testObject = new TestClass;

var_dump(property_exists("TestClass", "dynamic")); // boolean false, as expected
var_dump(property_exists($testObject, "dynamic")); // boolean false, same as above

$testObject->dynamic = null;
var_dump(property_exists($testObject, "dynamic")); // boolean true

unset($testObject->dynamic);
var_dump(property_exists($testObject, "dynamic")); // boolean false, again.

var_dump(property_exists($testObject, "declared")); // boolean true, as espected

unset($testObject->declared);
var_dump(property_exists($testObject, "declared")); // boolean true, even if has been unset()

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Stefan W ¶

10 years ago

If you are in a namespaced file, and you want to pass the class name as a string, you will have to include the full namespace for the class name - even from inside the same namespace:

<?
namespace MyNS;

class A {
    public $foo;
}

property_exists("A", "foo");          // false
property_exists("\\MyNS\\A", "foo");  // true
?>

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Nanhe Kumar ¶

10 years ago

<?php

class Student {

    protected $_name;
    protected $_email;
    

    public function __call($name, $arguments) {
        $action = substr($name, 0, 3);
        switch ($action) {
            case 'get':
                $property = '_' . strtolower(substr($name, 3));
                if(property_exists($this,$property)){
                    return $this->{$property};
                }else{
                    echo "Undefined Property";
                }
                break;
            case 'set':
                $property = '_' . strtolower(substr($name, 3));
                if(property_exists($this,$property)){
                    $this->{$property} = $arguments[0];
                }else{
                    echo "Undefined Property";
                }
                
                break;
            default :
                return FALSE;
        }
    }

}

$s = new Student();
$s->setName('Nanhe Kumar');
$s->setEmail('nanhe.kumar@gmail.com');
echo $s->getName(); //Nanhe Kumar
echo $s->getEmail(); // nanhe.kumar@gmail.com
$s->setAge(10); //Undefined Property
?>

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ewisuri [gmail] ¶

10 years ago

As of PHP 5.3.0, calling property_exists from a parent class sees private properties in sub-classes.

<?php
class P {
    public function test_prop($prop) { return property_exists($this, $prop); }
}

class Child extends P {
    private $prop1;
}

$child = new Child();
var_dump($child->test_prop('prop1')); //true, as of PHP 5.3.0

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falundir at gmail dot com ¶

7 years ago

If you want to test if declared *public* property was unset, you can use the following code:

<?php
class A {
    public $declared;
}

$a = new A();
$is_defined = array_key_exists('declared', (array)$a); //=>true

unset($a->declared);
$is_defined = array_key_exists('declared', (array)$a); //=>false
?>

down

@fitorec ¶

4 years ago

<?php

abstract class P {
  private $priv;
  static protected $static_prop;
  static function exists($prop = 'priv') {
      var_dump(property_exists(new static, $prop)); //true
  }
}

class S extends P {
  static protected $new_prop;
}
S::exists('new_prop');       // True
S::exists('static_prop');    // True
S::exists('priv');           // True

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saurabh dot agarwal89 at gmail dot com ¶

8 years ago

$a = array('a','b'=>'c');
print_r((object) $a);
var_dump( property_exists((object) $a,'0'));
var_dump( property_exists((object) $a,'b'));

OUTPUT:
stdClass Object
(
    [0] => a
    [b] => c
)
bool(false)
bool(true)

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-1

rnealxp at yahoo dot com ¶

4 years ago

For class constants, use defined() to check for their existence since property_exists() cannot be used.
<?php
class A{
    private static $c = 'C';
    const B = 'B';
}
if(property_exists('A','c')===true){
    echo 'y';
}else{
    echo 'n';
} //output: y
if(property_exists('A','B')===true){
    echo 'y';
}else{
    echo 'n';
} //output: n
if(defined('A::B')===true){
    echo 'y';
}else{
    echo 'n';
} //output: y
?>

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-3

Daniel dot Peder at infoset dot com ¶

7 years ago

declared properties cannot be unset
any set property does exist, even being set to null, regardless how it was set

<?php

class demo_property_exists {

    public $my_public;
    protected $my_protected;
    private $my_private;

    function __construct() {
        $this->dumper('before-constructed');
        $this->my_constructed_int = 123;
        $this->my_constructed_null = null;
        $this->dumper('after-constructed');
    }

    public function dumper($name) {
        printf("\n[%s] dump:\n", $name);

        foreach ($this->my_checklist() as $prop) {
            printf("[%s]:\t", $prop);
            var_dump(property_exists($this, $prop));
        }
    }

    public function unset_all() {
        foreach ($this->my_checklist() as $prop) {
            unset($this->$prop);
        }
    }

    private function my_checklist() {
        return array('my_public', 'my_protected', 'my_private', 'my_constructed_int', 'my_constructed_null', 'my_assigned_int', 'my_assigned_null',);
    }

}

$object = new demo_property_exists();
$object->dumper('before-assigned');
$object->my_assigned_int = 456;
$object->my_assigned_null = null;
$object->dumper('after-assigned');
$object->unset_all();
$object->dumper('after-unset');

/*
results:

[before-constructed] dump:
[my_public]:    bool(true)
[my_protected]: bool(true)
[my_private]:   bool(true)
[my_constructed_int]:   bool(false)
[my_constructed_null]:  bool(false)
[my_assigned_int]:      bool(false)
[my_assigned_null]:     bool(false)

[after-constructed] dump:
[my_public]:    bool(true)
[my_protected]: bool(true)
[my_private]:   bool(true)
[my_constructed_int]:   bool(true)
[my_constructed_null]:  bool(true)
[my_assigned_int]:      bool(false)
[my_assigned_null]:     bool(false)

[before-assigned] dump:
[my_public]:    bool(true)
[my_protected]: bool(true)
[my_private]:   bool(true)
[my_constructed_int]:   bool(true)
[my_constructed_null]:  bool(true)
[my_assigned_int]:      bool(false)
[my_assigned_null]:     bool(false)

[after-assigned] dump:
[my_public]:    bool(true)
[my_protected]: bool(true)
[my_private]:   bool(true)
[my_constructed_int]:   bool(true)
[my_constructed_null]:  bool(true)
[my_assigned_int]:      bool(true)
[my_assigned_null]:     bool(true)

[after-unset] dump:
[my_public]:    bool(true)
[my_protected]: bool(true)
[my_private]:   bool(true)
[my_constructed_int]:   bool(false)
[my_constructed_null]:  bool(false)
[my_assigned_int]:      bool(false)
[my_assigned_null]:     bool(false)

*/

down

-12

David Spector ¶

5 years ago

Just to clarify, property_exists only works for static properties. There is no corresponding const_exists function in PHP to do something similar for const names.

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