类型运算符instanceof在某些php书籍中貌似没有提到啊，在细说php中也只是提到没有细讲，摘抄下手册中的，以作备注。
instanceof 运算符是 PHP 5 引进的。在此之前用 is_a()，但是 is_a() 已经过时了，最好用 instanceof。
1、用来确定一个变量是否属于某个类的实例；
2、用来确定一个变量是否是继承自某一父类的子类的实例；
3、用来确定一个变量是否是实现了某个接口的对象的实例。
在 PHP 5.1.0之前，如果要检查的类名称不存在，instanceof 会调用 __autoload()。另外，如果该类没有被装载则会产生一个致命错误。可以通过使用动态类引用(dynamic class reference)或用一个包含类名的字符串变量来避开这种问题：
Example #6 避免 PHP 5.0 中 instanceof 引起的类名查找和致命错误问题
$d = 'NotMyClass';
var_dump($a instanceof $d); // no fatal error here
?>
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Zend Studio 13.0.1
Powerful PHP integrated development environment
WebStorm Mac version
Useful JavaScript development tools
SAP NetWeaver Server Adapter for Eclipse
Integrate Eclipse with SAP NetWeaver application server.
Safe Exam Browser
Safe Exam Browser is a secure browser environment for taking online exams securely. This software turns any computer into a secure workstation. It controls access to any utility and prevents students from using unauthorized resources.
mPDF
mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),
