异常(Exception):异常处理用于在指定的错误(异常)情况发生时改变脚本的正常流程。
当异常被触发时,通常会发生:
当前代码状态被保存 代码执行被切换到预定义的异常处理器函数 根据情况,处理器也许会从保存的代码状态重新开始执行代码,终止脚本执行,或从代码中另外的位置继续执行脚本我们将展示不同的错误处理方法:
异常的基本使用 创建自定义的异常处理器 多个异常 重新抛出异常 设置顶层异常处理器
<p class="sycode"> 基本使用 : </p> <p class="sycode"> Try, throw 和 catch 要避免上面例子出现的错误,我们需要创建适当的代码来处理异常。处理处理程序应当包括:Try - 使用异常的函数应该位于 " try " 代码块内。如果没有触发异常,则代码将照常继续执行。但异常被触发,会抛出一个异常 。 </p> <p class="sycode"> Throw - 这里规定如何触发异常。每一个 " throw " 必须对应至少一个 " catch " Catch - " catch " 代码块会捕获异常,并创建一个包含异常信息的对象 <? phpfunction inverse($x) { if ( ! $x) { throw new Exception( ' Division by zero. ' ); } else return 1 / $x;} try { echo inverse( 5 ) . " \n " ; echo inverse( 0 ) . " \n " ;} catch (Exception $e) { echo ' Caught exception: ' , $e -> getMessage(), " \n " ;} // Continue execution echo ' Hello World ' ; ?> </p>
~创建一个自定义的 Exception 类
创建自定义的异常处理程序非常简单。我们简单地创建了一个专门的类,当 PHP 中发生异常时,可调用其函数。该类必须是 exception 类的一个扩展。
这个自定义的 exception 类继承了 PHP 的 exception 类的所有属性,您可向其添加自定义的函数。
我们开始创建 exception 类:
<p class="sycode"> <? php class customException extends Exception { public function errorMessage() { // error message $errorMsg = ' Error on line ' .$ this -> getLine(). ' in ' .$ this -> getFile() . ' : <b> ' .$ this -> getMessage(). ' </b> is not a valid E-Mail address ' ; return $errorMsg; } }$email = " someone@example...com " ; try { // check if if (filter_var($email, FILTER_VALIDATE_EMAIL) === FALSE) { // throw exception if email is not valid throw new customException($email); } } catch (customException $e) { // display custom message echo $e -> errorMessage(); } ?> </p>
~多个异常
可以为一段脚本使用多个异常,来检测多种情况。
可以使用多个 if..else 代码块,或一个 switch 代码块,或者嵌套多个异常。这些异常能够使用不同的 exception 类,并返回不同的错误消息:
<p class="sycode"> <? php class customException extends Exception{ public function errorMessage(){ // error message $errorMsg = ' Error on line ' .$ this -> getLine(). ' in ' .$ this -> getFile(). ' : <b> ' .$ this -> getMessage(). ' </b> is not a valid E-Mail address ' ; return $errorMsg;}}$email = " someone@example.com " ; try { // check if if (filter_var($email, FILTER_VALIDATE_EMAIL) === FALSE) { // throw exception if email is not valid throw new customException($email); } // check for "example" in mail address if (strpos($email, " example " ) !== FALSE) { throw new Exception( " $email is an example e-mail " ); } } catch (customException $e) { echo $e -> errorMessage(); } catch (Exception $e) { echo $e -> getMessage(); } ?> </p>
~重新抛出异常
有时,当异常被抛出时,您也许希望以不同于标准的方式对它进行处理。可以在一个 "catch" 代码块中再次抛出异常。
脚本应该对用户隐藏系统错误。对程序员来说,系统错误也许很重要,但是用户对它们并不感兴趣。为了让用户更容易使用,您可以再次抛出带有对用户比较友好的消息的异常:
<p class="sycode"> <? php class customException extends Exception { public function errorMessage() { // error message $errorMsg = $ this -> getMessage(). ' is not a valid E-Mail address. ' ; return $errorMsg; } }$email = " someone@example.com " ; try { try { // check for "example" in mail address if (strpos($email, " example " ) !== FALSE) { // throw exception if email is not valid throw new Exception($email); } } catch(Exception $e) { //re-throw exception throw new customException($email); } } catch (customException $e) { // display custom message echo $e -> errorMessage(); } ?> </p>
~设置顶层异常处理器 (Top Level Exception Handler)
set_exception_handler() 函数可设置处理所有未捕获异常的用户定义函数。
<?phpfunction myException($exception){echo "<b>Exception:</b> " , $exception->getMessage();}set_exception_handler('myException');throw new Exception('Uncaught Exception occurred');?>
以上代码的输出应该类似这样:
Exception: Uncaught Exception occurred
在上面的代码中,不存在 "catch" 代码块,而是触发顶层的异常处理程序。应该使用此函数来捕获所有未被捕获的异常。
异常的规则 需要进行异常处理的代码应该放入 try 代码块内,以便捕获潜在的异常。 每个 try 或 throw 代码块必须至少拥有一个对应的 catch 代码块。 使用多个 catch 代码块可以捕获不同种类的异常。 可以在 try 代码块内的 catch 代码块中再次抛出(re-thrown)异常。
简而言之:如果抛出了异常,就必须捕获它。
~

Setting session cookie parameters in PHP can be achieved through the session_set_cookie_params() function. 1) Use this function to set parameters, such as expiration time, path, domain name, security flag, etc.; 2) Call session_start() to make the parameters take effect; 3) Dynamically adjust parameters according to needs, such as user login status; 4) Pay attention to setting secure and httponly flags to improve security.

The main purpose of using sessions in PHP is to maintain the status of the user between different pages. 1) The session is started through the session_start() function, creating a unique session ID and storing it in the user cookie. 2) Session data is saved on the server, allowing data to be passed between different requests, such as login status and shopping cart content.

How to share a session between subdomains? Implemented by setting session cookies for common domain names. 1. Set the domain of the session cookie to .example.com on the server side. 2. Choose the appropriate session storage method, such as memory, database or distributed cache. 3. Pass the session ID through cookies, and the server retrieves and updates the session data based on the ID.

HTTPS significantly improves the security of sessions by encrypting data transmission, preventing man-in-the-middle attacks and providing authentication. 1) Encrypted data transmission: HTTPS uses SSL/TLS protocol to encrypt data to ensure that the data is not stolen or tampered during transmission. 2) Prevent man-in-the-middle attacks: Through the SSL/TLS handshake process, the client verifies the server certificate to ensure the connection legitimacy. 3) Provide authentication: HTTPS ensures that the connection is a legitimate server and protects data integrity and confidentiality.

What’s still popular is the ease of use, flexibility and a strong ecosystem. 1) Ease of use and simple syntax make it the first choice for beginners. 2) Closely integrated with web development, excellent interaction with HTTP requests and database. 3) The huge ecosystem provides a wealth of tools and libraries. 4) Active community and open source nature adapts them to new needs and technology trends.

PHP and Python are both high-level programming languages that are widely used in web development, data processing and automation tasks. 1.PHP is often used to build dynamic websites and content management systems, while Python is often used to build web frameworks and data science. 2.PHP uses echo to output content, Python uses print. 3. Both support object-oriented programming, but the syntax and keywords are different. 4. PHP supports weak type conversion, while Python is more stringent. 5. PHP performance optimization includes using OPcache and asynchronous programming, while Python uses cProfile and asynchronous programming.

PHP is mainly procedural programming, but also supports object-oriented programming (OOP); Python supports a variety of paradigms, including OOP, functional and procedural programming. PHP is suitable for web development, and Python is suitable for a variety of applications such as data analysis and machine learning.

PHP originated in 1994 and was developed by RasmusLerdorf. It was originally used to track website visitors and gradually evolved into a server-side scripting language and was widely used in web development. Python was developed by Guidovan Rossum in the late 1980s and was first released in 1991. It emphasizes code readability and simplicity, and is suitable for scientific computing, data analysis and other fields.


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

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool

ZendStudio 13.5.1 Mac
Powerful PHP integrated development environment

WebStorm Mac version
Useful JavaScript development tools

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.

Notepad++7.3.1
Easy-to-use and free code editor