Pseudotypes and pseudovariables in PHP
1. Pseudo-types
There are three PHP pseudo-types, namely: 1, mixed type. 2. number digital type. 3. callbackCallback type.
1, mixed mixed type:
mixed indicates that a parameter can accept multiple different types, but not all types.
2, number numeric type:
The number parameter can accept integer integer type and floatFloating point type.
3, callback type:
For example, the call_user_func() function can receive a user-defined function as a parameter, which is php A built-in function. The callback function can not only be a function, but also a method of an object and a method of a static class. A php function is passed using the function namestring. Any built-in or user-defined function can be passed, except language structures such as array(), echo(), empty() ,eval(),exit(),isset(),list(),print(),unset(), etc.
If you want to pass in the method of an object, it needs to be passed in the form of an array. The array subscript 0 is the object name and the subscript 1 is the method name. If there is no static class instantiated as an object, to pass its method, replace the object name specified by the array 0 subscript with the name of the class.
In addition to ordinary user-defined functions, you can also use create_function to create an anonymous callback function.
Example::
<?php
//普通的回调函数
function my_callback_function(){
echo "my is callback function.";
}
//回调方法
class MyClass{
static function myCallbackMethod(){
echo "my is callback method.";
}
}
//num1:回调函数
call_user_func('my_callback_function');
//num2:静态类的方法
call_user_func(array('MyClass','myCallbackMethod'));
//num3:对象方法
$obj = new MyClass();
call_user_func(array($obj,'myCallbackMethod'));
//num4:静态类的方法（5.3.0以上）
call_user_func('MyClass::myCallbackMethod');
//num5:相对静态方法调用
class A {
public static function who(){
echo "A";
}
}
class B extends A {
public static function who(){
echo "B";
}
}
call_user_func(array('B','parent::who')); //输出B
//num6:调用时传入参数
function test($a,$b){
echo $a;
echo $b;
}
call_user_function('test','1','2'); //输出1 2
//num7:调用类方法传入参数
class a(){
function b($c){
echo $c;
}
}
call_user_func(array('a','b'),'1'); //输出1
//num8:call_user_func_array与call_user_func很相似，只不过换了一种方式传递参数，让参数结构更清晰：
function a($b,$c){
echo $b;
echo $c;
}
call_user_func_array('a',array('1','2')); //输出1 2
//num9:用call_user_func_array调用类内部方法
class A(){
function a($b,$c){
echo $b;
echo $c;
}
}
call_user_func_array(array('A','a'),array('1','2')); //输出1 2
//num10:call_user_func函数和call_user_func_array函数都支持引用，这让他们和普通的函数调用更趋于功能一致：
function a($b){
$b++;
}
$c=0;
call_user_func('a',$c); //输出1
call_user_func('a',array($c)); //输出2
2. Pseudo variables
$... in php is pseudo Variable means etc. This variable name is used when a function can accept any number of parameters.
The above is the detailed content of Pseudotypes and pseudovariables in PHP. For more information, please follow other related articles on the PHP Chinese website!
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
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
PHP 8.4 Installation and Upgrade guide for Ubuntu and Debian
Dec 24, 2024 pm 04:42 PM
PHP 8.4 brings several new features, security improvements, and performance improvements with healthy amounts of feature deprecations and removals. This guide explains how to install PHP 8.4 or upgrade to PHP 8.4 on Ubuntu, Debian, or their derivati
How To Set Up Visual Studio Code (VS Code) for PHP Development
Dec 20, 2024 am 11:31 AM
Visual Studio Code, also known as VS Code, is a free source code editor — or integrated development environment (IDE) — available for all major operating systems. With a large collection of extensions for many programming languages, VS Code can be c
Explain JSON Web Tokens (JWT) and their use case in PHP APIs.
Apr 05, 2025 am 12:04 AM
JWT is an open standard based on JSON, used to securely transmit information between parties, mainly for identity authentication and information exchange. 1. JWT consists of three parts: Header, Payload and Signature. 2. The working principle of JWT includes three steps: generating JWT, verifying JWT and parsing Payload. 3. When using JWT for authentication in PHP, JWT can be generated and verified, and user role and permission information can be included in advanced usage. 4. Common errors include signature verification failure, token expiration, and payload oversized. Debugging skills include using debugging tools and logging. 5. Performance optimization and best practices include using appropriate signature algorithms, setting validity periods reasonably,
PHP Program to Count Vowels in a String
Feb 07, 2025 pm 12:12 PM
A string is a sequence of characters, including letters, numbers, and symbols. This tutorial will learn how to calculate the number of vowels in a given string in PHP using different methods. The vowels in English are a, e, i, o, u, and they can be uppercase or lowercase. What is a vowel? Vowels are alphabetic characters that represent a specific pronunciation. There are five vowels in English, including uppercase and lowercase: a, e, i, o, u Example 1 Input: String = "Tutorialspoint" Output: 6 explain The vowels in the string "Tutorialspoint" are u, o, i, a, o, i. There are 6 yuan in total
How do you parse and process HTML/XML in PHP?
Feb 07, 2025 am 11:57 AM
This tutorial demonstrates how to efficiently process XML documents using PHP. XML (eXtensible Markup Language) is a versatile text-based markup language designed for both human readability and machine parsing. It's commonly used for data storage an
Explain late static binding in PHP (static::).
Apr 03, 2025 am 12:04 AM
Static binding (static::) implements late static binding (LSB) in PHP, allowing calling classes to be referenced in static contexts rather than defining classes. 1) The parsing process is performed at runtime, 2) Look up the call class in the inheritance relationship, 3) It may bring performance overhead.
What are PHP magic methods (__construct, __destruct, __call, __get, __set, etc.) and provide use cases?
Apr 03, 2025 am 12:03 AM
What are the magic methods of PHP? PHP's magic methods include: 1.\_\_construct, used to initialize objects; 2.\_\_destruct, used to clean up resources; 3.\_\_call, handle non-existent method calls; 4.\_\_get, implement dynamic attribute access; 5.\_\_set, implement dynamic attribute settings. These methods are automatically called in certain situations, improving code flexibility and efficiency.
PHP and Python: Comparing Two Popular Programming Languages
Apr 14, 2025 am 12:13 AM
PHP and Python each have their own advantages, and choose according to project requirements. 1.PHP is suitable for web development, especially for rapid development and maintenance of websites. 2. Python is suitable for data science, machine learning and artificial intelligence, with concise syntax and suitable for beginners.
