property_exists

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

property_exists — オブジェクトもしくはクラスにプロパティが存在するかどうかを調べる

説明

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

この関数は、与えられたプロパティ property が指定されたクラスに存在するかどうかを確認します。

注意:
isset() とは対照的に、プロパティの値が null の場合でも property_exists() は true を返します。

パラメータ

object_or_class: 確認するクラス名、もしくはクラスのオブジェクトを指定します。
property: プロパティ名を指定します。

戻り値

プロパティが存在している場合は true、存在していない場合に false を返します。

例

例1 property_exists() の例

<?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();

?>

注意

注意:
この関数を使うと、未知のクラスに対しては登録済みの autoloader を使用します。

注意:
property_exists() 関数は、マジックメソッド __get を使ってアクセスするプロパティを検出することはできません。

参考

method_exists() - クラスメソッドが存在するかどうかを確認する

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User Contributed Notes 6 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()

down

Stefan W ¶

11 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
?>

down

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
?>

down

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

down

saurabh dot agarwal89 at gmail dot com ¶

9 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)

down

-2

biziclop ¶

1 year ago

I needed a method for finding out if accessing a property outside a class is possible without errors/warnings, considering that the class might use the magic methods __isset/__get to simulate nonexistent properties.

<?php
// returns true if property is safely accessible publicly by using $obj->$prop
// Tested with PHP 5.1 - 8.2, see https://3v4l.org/QBTd1
function public_property_exists( $obj, $prop ){
  // allow magic $obj->__isset( $prop ) to execute if exists
  if( isset( $obj->$prop ))  return true;
  
  // no public/protected/private property exists with this name
  if( ! property_exists( $obj, $prop ))  return false;

  // the property exists, but is it public?
  $rp = new ReflectionProperty( $obj, $prop );
  return $rp->isPublic();
}

//// Test/demo
class C {
  public    $public    = "I’m public!";
  protected $protected = "I’m public!";
  private   $private   = "I’m public!";
  function __isset( $k ){
    return substr( $k, 0, 5 ) === 'magic';
  }
  function __get( $k ){
    if( $k === 'magic_isset_but_null')  return null;
    return "I’m {$k}!";
  }
}

$o = new C();
foreach( array(
  'public', 'protected', 'private',
  'magic', 'magic_isset_but_null',
  'missing'
) as $prop ){
  if( public_property_exists( $o, $prop ))
        echo "\$o->{$prop} is a public property, its value is: ",
             var_export( $o->$prop, true ), "\n";
  else  echo "\$o->{$prop} is not a public property.\n";
}
/*
$o->public    is a public property, its value is: 'I’m public!'
$o->protected is not a public property.
$o->private   is not a public property.
$o->magic     is a public property, its value is: 'I’m magic!'
$o->magic_isset_but_null is a public property, its value is: NULL
$o->missing   is not a public property.
*/

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