An example missing from the documentation is that `ReflectionClass::isInstantiable` will also return false for traits, as well as interfaces and abstract classes.
<?php
trait t {
// Optional trait methods and properties etc.
}
$reflectionClass = new ReflectionClass("t");
var_dump($reflectionClass->isInstantiable()); // bool(false)
?>
As for classes with private constructors, it is still possible to create an instance by either bypassing the constructor using `ReflectionClass::newInstanceWithoutConstructor`, or by ensuring the class has a method which can create a new instance.
<?php
class p {
private function __construct() {
// Optional constructor logic - not called when ReflectionClass::newInstanceWithoutConstructor is used.
}
public static function create() {
return new p;
}
// Optional methods and properties etc.
}
// Class is not classed as instantiable.
$reflectionClass = new ReflectionClass("p");
var_dump($reflectionClass->isInstantiable()); // bool(false)
// We're still able to create an instance using one of the two methods.
$p = p::create();
$p = $reflectionClass->newInstanceWithoutConstructor();
?>
The same is also true for protected constructors, however, the class can be instantiated from either parent or child methods, depending on where the constructor is defined.
<?php
class p {
protected function __construct() {
// Optional constructor logic.
}
public static function create( $class = "" ) {
if (!$class) {
$class = get_called_class();
}
return new $class;
}
// Optional parent methods and properties etc.
}
class c extends p
{
// Optional child methods and properties etc.
}
// Both child and parent static methods have access to each other's protected constructor.
$p = c::create("p");
$c = p::create("c");
// Both are still not classed as being instantiable.
$reflectionClassP = new ReflectionClass("p");
$reflectionClassC = new ReflectionClass("c");
var_dump($reflectionClassP->isInstantiable()); // bool(false)
var_dump($reflectionClassC->isInstantiable()); // bool(false)
// We're still able to bypass the constructor and create an instance for each.
$p = $reflectionClassP->newInstanceWithoutConstructor();
$c = $reflectionClassC->newInstanceWithoutConstructor();
?>
ReflectionClass::isInstantiable
(PHP 5, PHP 7, PHP 8)
ReflectionClass::isInstantiable — 检查类是否可实例化
参数
此函数没有参数。
返回值
成功时返回 true， 或者在失败时返回 false。
示例
示例 #1 ReflectionClass::isInstantiable() 示例
<?php
class C { }
interface iface {
function f1();
}
class ifaceImpl implements iface {
function f1() {}
}
abstract class abstractClass {
function f1() { }
abstract function f2();
}
class D extends abstractClass {
function f2() { }
}
trait T {
function f1() {}
}
class privateConstructor {
private function __construct() { }
}
$classes = array(
"C",
"iface",
"ifaceImpl",
"abstractClass",
"D",
"T",
"privateConstructor",
);
foreach($classes as $class ) {
$reflectionClass = new ReflectionClass($class);
echo "Is $class instantiable? ";
var_dump($reflectionClass->isInstantiable());
}
?>以上示例会输出：
Is C instantiable? bool(true) Is iface instantiable? bool(false) Is ifaceImpl instantiable? bool(true) Is abstractClass instantiable? bool(false) Is D instantiable? bool(true) Is T instantiable? bool(false) Is privateConstructor instantiable? bool(false)
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shaun at slickdesign dot com dot au ¶
6 years ago
