In case this saves anyone any time, I spent ages working out why the following didn't work:
class MyClass
{
private $foo = FALSE;
public function __construct()
{
$this->$foo = TRUE;
echo($this->$foo);
}
}
$bar = new MyClass();
giving "Fatal error: Cannot access empty property in ...test_class.php on line 8"
The subtle change of removing the $ before accesses of $foo fixes this:
class MyClass
{
private $foo = FALSE;
public function __construct()
{
$this->foo = TRUE;
echo($this->foo);
}
}
$bar = new MyClass();
I guess because it's treating $foo like a variable in the first example, so trying to call $this->FALSE (or something along those lines) which makes no sense. It's obvious once you've realised, but there aren't any examples of accessing on this page that show that.
Propriétés
Les variables au sein d'une classe sont appelées propriétés.
On peut également les retrouver sous d'autres dénominations tel que
champs, mais pour cette documentation
propriété sera utilisé.
Elles sont définies en utilisant un des mots-clés public,
protected, ou private, suivi
optionnellement, à partir de PHP 7.4, d'une déclaration de type,
suivi d'une déclaration classique de variable.
Cette déclaration peut comprendre une initialisation, mais celle-ci doit
être une valeur constante
Référez-vous à Visibilité pour plus
d'informations sur la signification
de public, protected,
et private.
Note:
Une manière alternative et non recommandé de déclarer une propriété de classe, car c'est pour maintenir la la rétrocompatibilité avec PHP 4, est d'utiliser le mot-clé
var. La propriété sera traitée comme si elle avait été déclarée commepublic.
Au sein des méthodes de classes, les propriétés non statiques peuvent être
appelées en utilisant la syntaxe -> (opérateur de l'objet) :
$this->property (où property est le
nom de la propriété). Les propriétés statiques peuvent être appelées en
utilisant la syntaxe :: (deux doubles points) :
self::$property. Reportez-vous à la documentation sur
le mot clé statique pour plus d'informations
sur la différence entre les propriétés statiques et non statiques.
La pseudo-variable $this est disponible au sein de n'importe quelle méthode, lorsque cette méthode est appelée au sein d'un objet. $this est la valeur de l'objet appelant.
Exemple #1 Déclarations de propriétés
<?php
class SimpleClass
{
public $var1 = 'hello ' . 'world';
public $var2 = <<<EOD
hello world
EOD;
public $var3 = 1+2;
// déclaration de propriété invalide :
public $var4 = self::myStaticMethod();
public $var5 = $myVar;
// Déclarations valides de propriétés :
public $var6 = myConstant;
public $var7 = [true, false];
public $var8 = <<<'EOD'
hello world
EOD;
}
?>
Note:
Il existe des fonctions diverses qui permettent de gérer des classes et des objets. Voir la référence sur les Fonctions Classes/Objets.
Déclarations des types
À partir de PHP 7.4.0, les définitions de propriétés peuvent inclure une
Déclarations de type,
avec l'exception du type callable.
Exemple #2 Exemple de propriétés typées
<?php
class User
{
public int $id;
public ?string $name;
public function __construct(int $id, ?string $name)
{
$this->id = $id;
$this->name = $name;
}
}
$user = new User(1234, null);
var_dump($user->id);
var_dump($user->name);
?>
L'exemple ci-dessus va afficher :
int(1234) NULL
Les propriétés typés doivent être initialisées avant d'y accéder, sinon, une Error sera émise.
Exemple #3 Accès aux propriétés
<?php
class Shape
{
public int $numberOfSides;
public string $name;
public function setNumberOfSides(int $numberOfSides): void
{
$this->numberOfSides = $numberOfSides;
}
public function setName(string $name): void
{
$this->name = $name;
}
public function getNumberOfSides(): int
{
return $this->numberOfSides;
}
public function getName(): string
{
return $this->name;
}
}
$triangle = new Shape();
$triangle->setName("triangle");
$triangle->setNumberofSides(3);
var_dump($triangle->getName());
var_dump($triangle->getNumberOfSides());
$circle = new Shape();
$circle->setName("circle");
var_dump($circle->getName());
var_dump($circle->getNumberOfSides());
?>
L'exemple ci-dessus va afficher :
string(8) "triangle" int(3) string(6) "circle" Fatal error: Uncaught Error: Typed property Shape::$numberOfSides must not be accessed before initialization
add a note
User Contributed Notes 9 notes
Anonymous ¶
9 years ago
anca at techliminal dot com ¶
5 years ago
You can access property names with dashes in them (for example, because you converted an XML file to an object) in the following way:
<?php
$ref = new StdClass();
$ref->{'ref-type'} = 'Journal Article';
var_dump($ref);
?>
Anonymous ¶
10 years ago
$this can be cast to array. But when doing so, it prefixes the property names/new array keys with certain data depending on the property classification. Public property names are not changed. Protected properties are prefixed with a space-padded '*'. Private properties are prefixed with the space-padded class name...
<?php
class test
{
public $var1 = 1;
protected $var2 = 2;
private $var3 = 3;
static $var4 = 4;
public function toArray()
{
return (array) $this;
}
}
$t = new test;
print_r($t->toArray());
/* outputs:
Array
(
[var1] => 1
[ * var2] => 2
[ test var3] => 3
)
*/
?>
This is documented behavior when converting any object to an array (see </language.types.array.php#language.types.array.casting> PHP manual page). All properties regardless of visibility will be shown when casting an object to array (with exceptions of a few built-in objects).
To get an array with all property names unaltered, use the 'get_object_vars($this)' function in any method within class scope to retrieve an array of all properties regardless of external visibility, or 'get_object_vars($object)' outside class scope to retrieve an array of only public properties (see: </function.get-object-vars.php> PHP manual page).
php at webflips dot net ¶
7 years ago
Heredoc IS valid as of PHP 5.3 and this is documented in the manual at http://php.net/manual/en/language.types.string.php#language.types.string.syntax.heredoc
Only heredocs containing variables are invalid because then it becomes dynamic.
zzzzBov ¶
10 years ago
Do not confuse php's version of properties with properties in other languages (C++ for example). In php, properties are the same as attributes, simple variables without functionality. They should be called attributes, not properties.
Properties have implicit accessor and mutator functionality. I've created an abstract class that allows implicit property functionality.
<?php
abstract class PropertyObject
{
public function __get($name)
{
if (method_exists($this, ($method = 'get_'.$name)))
{
return $this->$method();
}
else return;
}
public function __isset($name)
{
if (method_exists($this, ($method = 'isset_'.$name)))
{
return $this->$method();
}
else return;
}
public function __set($name, $value)
{
if (method_exists($this, ($method = 'set_'.$name)))
{
$this->$method($value);
}
}
public function __unset($name)
{
if (method_exists($this, ($method = 'unset_'.$name)))
{
$this->$method();
}
}
}
?>
after extending this class, you can create accessors and mutators that will be called automagically, using php's magic methods, when the corresponding property is accessed.
Ashley Dambra ¶
7 years ago
Updated method objectThis() to transtypage class array properties or array to stdClass.
Hope it help you.
public function objectThis($array = null) {
if (!$array) {
foreach ($this as $property_name => $property_values) {
if (is_array($property_values) && !empty($property_values)) {
$this->{$property_name} = $this->objectThis($property_values);
} else if (is_array($property_values) && empty($property_values)) {
$this->{$property_name} = new stdClass();
}
}
} else {
$object = new stdClass();
foreach ($array as $index => $values) {
if (is_array($values) && empty($values)) {
$object->{$index} = new stdClass();
} else if (is_array($values)) {
$object->{$index} = $this->objectThis($values);
} else {
$object->{$index} = $values;
}
}
return $object;
}
}
Markus Zeller ¶
4 years ago
Accessing a property without any value initialized will give NULL.
class foo
{
private $bar;
public __construct()
{
var_dump($this->bar); // null
}
}
AshleyDambra at live dot com ¶
7 years ago
Add this method to you class in order to 'transtypage' all the array properties into stdClass();
Hope it help you.
public function objectThis($object = null) {
if (!$object) {
foreach ($this as $property_name => $property_values) {
if (is_array($property_values)) {
$this->{$property_name} = $this->objectThis($property_values);
}
}
} else {
$object2 = new stdClass();
foreach ($object as $index => $values) {
if (is_array($values)) {
$object2->{$index} = $this->objectThis($values);
} else {
$object2->{$index} = $values;
}
}
return $object2;
}
}
Anonymous ¶
6 years ago
In case this saves anyone any time, I spent ages working out why the following didn't work:
class MyClass
{
private $foo = FALSE;
public function __construct()
{
$this->$foo = TRUE;
echo($this->$foo);
}
}
$bar = new MyClass();
giving "Fatal error: Cannot access empty property in ...test_class.php on line 8"
The subtle change of removing the $ before accesses of $foo fixes this:
class MyClass
{
private $foo = FALSE;
public function __construct()
{
$this->foo = TRUE;
echo($this->foo);
}
}
$bar = new MyClass();
I guess because it's treating $foo like a variable in the first example, so trying to call $this->FALSE (or something along those lines) which makes no sense. It's obvious once you've realised, but there aren't any examples of accessing on this page that show that.
[Editor's note: Removed copy of note by zzzzBov]
