# 类与对象

* [class_alias - 为一个类创建别名](#classalias)
* [class_exists - 检查类是否已定义](#classexists)
* [get_called_class - 获取后期静态绑定类的名称](#getcalledclass)
* [get_class_methods - 返回由类的方法名组成的数组](#getclassmethods)
* [get_class_vars - 返回由类的默认属性组成的数组](#getclassvars)
* [get_class - 返回对象的类名](#getclass)
* [get_declared_classes - 返回由已定义类的名字所组成的数组](#getdeclaredclasses)
* [get_declared_interfaces - 返回一个数组包含所有已声明的接口](#getdeclaredinterfaces)
* [get_declared_traits - 返回所有已定义的 Trait 的数组](#getdeclaredtraits)
* [get_object_vars - 返回由对象属性组成的关联数组](#getobjectvars)
* [get_parent_class - 返回对象或类的父类名](#getparentclass)
* [interface_exists - 检查接口是否已被定义](#interfaceexists)
* [is_a - 如果对象属于该类或该类是此对象的父类则返回 true](#isa)
* [is_subclass_of - 如果此对象是该类的子类，则返回 true](#issubclassof)
* [method_exists - 检查类的方法是否存在](#methodexists)
* [property_exists - 检查对象或类是否具有该属性](#propertyexists)
* [trait_exists - 检查指定的 Trait 是否存在](#traitexists)

## class_alias

```php
<?php

class Foo
{
    //
}

var_dump(class_alias('Foo', 'Bar')); // bool(true)

$foo = new Foo();
$bar = new Bar();

var_dump($foo == $bar);              // bool(true)
var_dump($foo === $bar);             // bool(false)
var_dump($foo instanceof Foo);       // bool(true)
var_dump($foo instanceof Bar);       // bool(true)
var_dump($bar instanceof Foo);       // bool(true)
var_dump($bar instanceof Bar);       // bool(true)

```

## class_exists

```php
<?php

class Foo
{
    //
}

var_dump(class_exists('Foo'));      // bool(true)
var_dump(class_exists('Bar'));      // bool(false)

```

## get_called_class

```php
<?php

class Foo
{
    /**
     * Return the class name of the late static binding.
     *
     * @param  void
     * @return string
     */
    public static function method(): string
    {
        return get_called_class();
    }

    /**
     * Return the class name of the late static binding.
     *
     * @param  void
     * @return string
     */
    public static function call(): string
    {
        return static::class;
    }
}

class Bar extends Foo
{
}

var_dump(Foo::method()); // string(3) "Foo"
var_dump(Bar::method()); // string(3) "Bar"
var_dump(Foo::call());   // string(3) "Foo"
var_dump(Bar::call());   // string(3) "Bar"

```

## get_class_methods

```php
<?php

class Foo
{
    /**
     * Public method.
     *
     * @param  void
     * @return void
     */
    public static function public()
    {
        //
    }

    /**
     * Protected method.
     *
     * @param  void
     * @return void
     */
    protected static function protected()
    {
        //
    }

    /**
     * Private method.
     *
     * @param  void
     * @return void
     */
    private static function private()
    {
        //
    }

    /**
     * Return all visibility methods.
     *
     * @param  void
     * @return array
     */
    public static function method(): array
    {
        return get_class_methods(static::class);
    }
}

class Bar extends Foo
{
    //
}

$foo = new Foo();
$bar = new Bar();

var_dump(get_class_methods('Foo')); // array(2) { [0]=> string(6) "public" [1]=> string(6) "method" }
var_dump(get_class_methods('Bar')); // array(2) { [0]=> string(6) "public" [1]=> string(6) "method" }
var_dump(get_class_methods($foo));  // array(2) { [0]=> string(6) "public" [1]=> string(6) "method" }
var_dump(get_class_methods($bar));  // array(2) { [0]=> string(6) "public" [1]=> string(6) "method" }
var_dump(Foo::method());            // array(4) { [0]=> string(6) "public" [1]=> string(9) "protected" [2]=> string(7) "private" [3]=> string(6) "method" }
var_dump(Bar::method());            // array(4) { [0]=> string(6) "public" [1]=> string(9) "protected" [2]=> string(7) "private" [3]=> string(6) "method" }

```

## get_class_vars

```php
<?php

class Foo
{
    /**
     * Public property.
     *
     * @var string
     */
    public string $public = 'public';

    /**
     * Protected property.
     *
     * @var string
     */
    protected string $protected = 'protected';

    /**
     * Private property.
     *
     * @var string
     */
    private $private;

    /**
     * Return all visibility properties.
     *
     * @param  void
     * @return array
     */
    public static function method(): array
    {
        return get_class_vars(static::class);
    }
}

class Bar extends Foo
{
    //
}

var_dump(get_class_vars('Foo')); // array(1) { ["public"]=> string(6) "public" }
var_dump(get_class_vars('Bar')); // array(1) { ["public"]=> string(6) "public" }
var_dump(Foo::method());         // array(3) { ["public"]=> string(6) "public" ["protected"]=> string(9) "protected" ["private"]=> NULL }
var_dump(Bar::method());         // array(3) { ["public"]=> string(6) "public" ["protected"]=> string(9) "protected" ["private"]=> NULL }

```

## get_class

```php
<?php

class Foo
{
    /**
     * Return the class name of the specified object.
     *
     * @param  void
     * @return string
     */
    public function method(): string
    {
        return get_class($this);
    }
}

class Bar extends Foo
{
    //
}

$foo = new Foo();
$bar = new Bar();

var_dump(get_class($foo)); // string(3) "Foo"
var_dump(get_class($bar)); // string(3) "Bar"
var_dump($foo->method());  // string(3) "Foo"
var_dump($bar->method());  // string(3) "Bar"

```

## get_declared_classes

```php
<?php

var_dump(get_declared_classes());

```

## get_declared_interfaces

```php
<?php

var_dump(get_declared_interfaces());

```

## get_declared_traits

```php
<?php

var_dump(get_declared_traits());

```

## get_object_vars

```php
<?php

class Foo
{
    /**
     * Public property.
     *
     * @var string
     */
    public string $public = 'public';

    /**
     * Protected property.
     *
     * @var string
     */
    protected string $protected = 'protected';

    /**
     * Private property.
     *
     * @var string
     */
    private $private;

    /**
     * Return all visibility properties.
     *
     * @param  void
     * @return array
     */
    public function method(): array
    {
        return get_object_vars($this);
    }
}

class Bar extends Foo
{
    //
}

$foo = new Foo();
$bar = new Bar();

var_dump(get_object_vars($foo)); // array(1) { ["public"]=> string(6) "public" }
var_dump(get_object_vars($bar)); // array(1) { ["public"]=> string(6) "public" }
var_dump($foo->method());        // array(3) { ["public"]=> string(6) "public" ["protected"]=> string(9) "protected" ["private"]=> NULL }
var_dump($bar->method());        // array(3) { ["public"]=> string(6) "public" ["protected"]=> string(9) "protected" ["private"]=> NULL }

```

## get_parent_class

```php
<?php

class Foo
{
    /**
     * Return the parent class name of the specified class.
     *
     * @param  void
     * @return string|bool
     */
    public static function method()
    {
        return get_parent_class(static::class);
    }
}

class Bar extends Foo
{
    //
}

$foo = new Foo();
$bar = new Bar();

var_dump(get_parent_class('Foo')); // bool(false)
var_dump(get_parent_class('Bar')); // string(3) "Foo"
var_dump(get_parent_class($foo));  // bool(false)
var_dump(get_parent_class($bar));  // string(3) "Foo"
var_dump(Foo::method());           // bool(false)
var_dump(Bar::method());           // string(3) "Foo"

```

## interface_exists

```php
<?php

interface Foo
{
    //
}

var_dump(interface_exists('Foo')); // bool(true)
var_dump(interface_exists('Bar')); // bool(false)

```

## is_a

```php
<?php

class Foo
{
    //
}

class Bar extends Foo
{
    //
}

$foo = new Foo();
$bar = new Bar();

var_dump(is_a('Foo', 'Foo', false)); // bool(false)
var_dump(is_a('Foo', 'Bar', false)); // bool(false)
var_dump(is_a('Bar', 'Foo', false)); // bool(false)
var_dump(is_a('Bar', 'Bar', false)); // bool(false)
var_dump(is_a('Foo', 'Foo', true));  // bool(true)
var_dump(is_a('Foo', 'Bar', true));  // bool(false)
var_dump(is_a('Bar', 'Foo', true));  // bool(true)
var_dump(is_a('Bar', 'Bar', true));  // bool(true)
var_dump(is_a($foo, 'Foo'));         // bool(true)
var_dump(is_a($foo, 'Bar'));         // bool(false)
var_dump(is_a($bar, 'Foo'));         // bool(true)
var_dump(is_a($bar, 'Bar'));         // bool(true)

```

## is_subclass_of

```php
<?php

class Foo
{
    //
}

class Bar extends Foo
{
    //
}

$foo = new Foo();
$bar = new Bar();

var_dump(is_subclass_of('Foo', 'Foo', false)); // bool(false)
var_dump(is_subclass_of('Foo', 'Bar', false)); // bool(false)
var_dump(is_subclass_of('Bar', 'Foo', false)); // bool(false)
var_dump(is_subclass_of('Bar', 'Bar', false)); // bool(false)
var_dump(is_subclass_of('Foo', 'Foo', true));  // bool(false)
var_dump(is_subclass_of('Foo', 'Bar', true));  // bool(false)
var_dump(is_subclass_of('Bar', 'Foo', true));  // bool(true)
var_dump(is_subclass_of('Bar', 'Bar', true));  // bool(false)
var_dump(is_subclass_of($foo, 'Foo'));         // bool(false)
var_dump(is_subclass_of($foo, 'Bar'));         // bool(false)
var_dump(is_subclass_of($bar, 'Foo'));         // bool(true)
var_dump(is_subclass_of($bar, 'Bar'));         // bool(false)

```

## method_exists

```php
<?php

class Foo
{
    /**
     * Public method.
     *
     * @param  void
     * @return void
     */
    public static function public()
    {
        //
    }

    /**
     * Protected method.
     *
     * @param  void
     * @return void
     */
    protected static function protected()
    {
        //
    }

    /**
     * Private method.
     *
     * @param  void
     * @return void
     */
    private static function private()
    {
        //
    }
}

class Bar extends Foo
{
    //
}

$foo = new Foo();
$bar = new Bar();

var_dump(method_exists('Foo', 'public'));    // bool(true)
var_dump(method_exists('Foo', 'protected')); // bool(true)
var_dump(method_exists('Foo', 'private'));   // bool(true)
var_dump(method_exists('Bar', 'public'));    // bool(true)
var_dump(method_exists('Bar', 'protected')); // bool(true)
var_dump(method_exists('Bar', 'private'));   // bool(false)
var_dump(method_exists($foo, 'public'));     // bool(true)
var_dump(method_exists($foo, 'protected'));  // bool(true)
var_dump(method_exists($foo, 'private'));    // bool(true)
var_dump(method_exists($bar, 'public'));     // bool(true)
var_dump(method_exists($bar, 'protected'));  // bool(true)
var_dump(method_exists($bar, 'private'));    // bool(true)

```

## property_exists

```php
<?php

class Foo
{
    /**
     * Public property.
     *
     * @var string
     */
    public string $public = 'public';

    /**
     * Protected property.
     *
     * @var string
     */
    protected string $protected = 'protected';

    /**
     * Private property.
     *
     * @var string
     */
    private $private;
}

class Bar extends Foo
{
    //
}

$foo = new Foo();
$bar = new Bar();

var_dump(property_exists('Foo', 'public'));    // bool(true)
var_dump(property_exists('Foo', 'protected')); // bool(true)
var_dump(property_exists('Foo', 'private'));   // bool(true)
var_dump(property_exists('Bar', 'public'));    // bool(true)
var_dump(property_exists('Bar', 'protected')); // bool(true)
var_dump(property_exists('Bar', 'private'));   // bool(false)
var_dump(property_exists($foo, 'public'));     // bool(true)
var_dump(property_exists($foo, 'protected'));  // bool(true)
var_dump(property_exists($foo, 'private'));    // bool(true)
var_dump(property_exists($bar, 'public'));     // bool(true)
var_dump(property_exists($bar, 'protected'));  // bool(true)
var_dump(property_exists($bar, 'private'));    // bool(false)

```

## trait_exists

```php
<?php

trait Foo
{
    //
}

var_dump(trait_exists('Foo')); // bool(true)
var_dump(trait_exists('Bar')); // bool(false)

```