Home Backend Development PHP Tutorial php中debug_backtrace、debug_print_backtrace和匿名函数用法实例_PHP

php中debug_backtrace、debug_print_backtrace和匿名函数用法实例_PHP

May 31, 2016 pm 06:16 PM
php

本文实例讲述了php中debug_backtrace、debug_print_backtrace和匿名函数用法。分享给大家供大家参考。具体分析如下:

debug_print_backtrace() 是一个很低调的函数,很少有人注意过它.

不过当我们对着一个对象调用另一个对象再调用其它的对象和文件中的一个函数出错时,它正在一边笑呢.

debug_print_backtrace() 可以打印出一个页面的调用过程,从哪儿来到哪儿去一目了然.不过这是一个PHP5的专有函数,好在pear中已经有了实现.

一、debug_backtrace 它可以回溯跟踪函数的调用信息,可以说是一个调试利器,代码如下:

代码如下:

one(); 
function one() {    two();     } 
function two() {    three();  } 
function three() {    print_r( debug_backtrace() );   } 
/*输出: 
Array( 
     [0] => Array        ( 
            [file] => D:apmservwwwhtdocstestdebugindex.php 
            [line] => 10 
            [function] => three 
            [args] => Array                (                ) 
      ), 
      [1] => Array        ( 
           [file] => D:apmservwwwhtdocstestdebugindex.php 
           [line] => 6 
           [function] => two 
           [args] => Array                (                ) 
      ), 
      [2] => Array        ( 
           [file] => D:apmservwwwhtdocstestdebugindex.php 
           [line] => 3 
           [function] => one 
           [args] => Array                (                ) 
      ) 
)*/


二、debug_print_backtrace 它与之不同的是它会直接打印回溯信息.

三、匿名函数

从PHP 5.3开始新增了匿名函数(Anonymous functions),也叫闭包函数(closures),关键字 use 同时也在匿名函数中.

先看一下匿名函数的示例,作为回调函数的参数,代码如下:

代码如下:

echo preg_replace_callback('~-([a-z])~', function ($match) { 
    return strtoupper($match[1]); 
    }, 'hello-world'
); 
// 输出 helloWorld 
?>


连接闭包和外界变量的关键字:USE

闭包可以保存所在代码块上下文的一些变量和值,PHP在默认情况下,匿名函数不能调用所在代码块的上下文变量,而需要通过使用use关键字,代码如下:

代码如下:

function test(){ 
    $num = 2; 
    $array = array(1,2,3,4,5,6,7,8); 
    print_r(array_filter($array, function($param)  use ($num){ 
    return $param % intval($num) ==0; }) 
);}
test();

希望本文所述对大家的PHP程序设计有所帮助。

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

PHP 8.4 Installation and Upgrade guide for Ubuntu and Debian 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

7 PHP Functions I Regret I Didn't Know Before 7 PHP Functions I Regret I Didn't Know Before Nov 13, 2024 am 09:42 AM

If you are an experienced PHP developer, you might have the feeling that you’ve been there and done that already.You have developed a significant number of applications, debugged millions of lines of code, and tweaked a bunch of scripts to achieve op

How To Set Up Visual Studio Code (VS Code) for PHP Development 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. 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 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? 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::). 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? 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.

See all articles