ReflectionClass::isInstantiable

(PHP 5, PHP 7, PHP 8)

ReflectionClass::isInstantiable — 检查类是否可实例化

说明

public ReflectionClass::isInstantiable(): 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

示例 #1 ReflectionClass::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

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User Contributed Notes 1 note

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2
shaun at slickdesign dot com dot au
4 years ago
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();
?>
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