property_exists

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()<?phpclass TestClass {    public $declared = null;    }$testObject = new TestClass;var_dump(property_exists("TestClass", "dynamic")); // boolean false, as expectedvar_dump(property_exists($testObject, "dynamic")); // boolean false, same as above$testObject->dynamic = null;var_dump(property_exists($testObject, "dynamic")); // boolean trueunset($testObject->dynamic);var_dump(property_exists($testObject, "dynamic")); // boolean false, again.var_dump(property_exists($testObject, "declared")); // boolean true, as espectedunset($testObject->declared);var_dump(property_exists($testObject, "declared")); // boolean true, even if has been unset()

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

<?phpclass 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 Kumarecho $s->getEmail(); // nanhe.kumar@gmail.com$s->setAge(10); //Undefined Property?>

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

$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)

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/QBTd1function 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/democlass 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.*/