ReflectionClass::isInstantiable()

(PHP 5, PHP 7)

检查类是否可实例化

说明

publicReflectionClass::isInstantiable(void): bool

检查这个类是否可实例化。

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。

范例

Example #1ReflectionClass::isInstantiable()例子

<?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() { }
}
class privateConstructor {
    private function __construct() { }
}
$classes = array(
    "C",
    "iface",
    "ifaceImpl",
    "abstractClass",
    "D",
    "privateConstructor",
);
foreach($classes  as $class ) {
    $reflectionClass = new ReflectionClass($class);
    echo "Is $class instantiable?  ";
    var_dump($reflectionClass->IsInstantiable()); 
}
?>

以上例程会输出：

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 privateConstructor instantiable?  bool(false)

参见

• ReflectionClass::isInstance() 检查类的实例

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();
?>