PHP exception error handling mechanism and error handling (1/2)

Home

Backend Development

PHP Tutorial

PHP exception error handling mechanism and error handling (1/2)_PHP tutorial

WBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWB

Jul 13, 2016 am 10:55 AM

catch php try and exist deal with abnormal us have mechanism use this mistake

The most common error mechanism we use in PHP is try catch{}, which can easily catch errors. However, PHP also provides error viewing and error closing for many things. This can be found in php.ini During processing, you can also add error_display(0); at the beginning of the file to not display errors

The code is as follows

Copy code

代码如下	复制代码
$a = fopen('test.txt','r'); //这里并没有对文件进行判断就打开了，如果文件不存在就会报错 ?>

$a = fopen('test.txt','r');

//The file is opened here without judging it. If the file does not exist, an error will be reported

代码如下	复制代码
if(file_exists('test.txt')){ $f=fopen('test.txt','r'); //使用完后关闭 fclose($f); } ?>

Then the correct way to write it should be as follows:

The code is as follows	Copy code

代码如下	复制代码
if(!file_exists('aa.txt')){ die('文件不存在'); } else { //执行操作 } //如果上面die()被触发，那么这里echo接不被执行 echo 'ok';

if(file_exists('test.txt')){

$f=fopen('test.txt','r');

//Close after use

代码如下	复制代码
file_exits('aaa.txt') or die('文件不存在'); echo 'ok';

fclose($f); <🎜> } <🎜> ?>

1. Three methods of PHP error handling A. Simple die() statement; Equivalent to exit(); Example:

The code is as follows	Copy code
if(!file_exists('aa.txt')){ die('File does not exist'); } else { //Perform operation } //If die() above is triggered, then the echo connection here will not be executed echo 'ok';

Concise writing:

The code is as follows	Copy code
file_exits('aaa.txt') or die('File does not exist'); echo 'ok';

B. Custom errors and error triggers

1. Error handler (custom error, generally used for syntax error handling)
Create a custom error function (handler) that must be able to handle at least two parameters (error_level and errormessage), but can accept up to five parameters (error_file, error_line, error_context)
Syntax:

function error_function($error_level,$error_message,$error_file,$error_line,$error_context)
//After creation, you need to rewrite the set_error_handler(); function
set_error_handler('error_function',E_WARNING); //Here error_function corresponds to the custom handler name created above, and the second parameter is the error level using the custom error handler;

Error reporting level (just understand it)

These error reporting levels are different types of errors that error handlers are designed to handle:

Value Constant Description
2 E_WARNING Nonfatal run-time error. Do not pause script execution.
8 E_NOTICE Run-time notification.

Script discovery errors may occur, but may also occur while the script is running normally.

256 E_USER_ERROR Fatal user-generated error. This is similar to E_ERROR set by the programmer using the PHP function trigger_error().
512 E_USER_WARNING Non-fatal user-generated warning. This is similar to the E_WARNING set by the programmer using the PHP function trigger_error().
1024 E_USER_NOTICE User-generated notification. This is similar to E_NOTICE set by the programmer using the PHP function trigger_error().
4096 E_RECOVERABLE_ERROR Trapable fatal error. Like E_ERROR, but can be caught by a user-defined handler. (see set_error_handler())
8191 E_ALL All errors and warnings except level E_STRICT.

(In PHP 6.0, E_STRICT is part of E_ALL)

2. Error trigger (generally used to handle logical errors)
Requirement: For example, if you want to receive an age, if the number is greater than 120, it is considered an error
Traditional method:

if($age>120){
echo 'Wrong age';exit();
}

Use triggers:

if($age>120){
//trigger_error('error message'[,'error level']); The error level here is optional and is used to define the level of the error
//User-defined levels include the following three types: E_USER_WARNING, E_USER_ERROR, E_USER_NOTICE
trigger_error('age error');//This is the default error handling method of the calling system, we can also use a custom processor
}
//Custom processor, same as above
function myerror($error_level,$error_message){
echo 'error text';
}
//At the same time, the system default processing function needs to be changed
set_error_handler('myerror',E_USER_WARNING);//Same as above, the first parameter is the name of the custom function, and the second parameter is the error level [The error levels here are usually the following three: E_USER_WARNING, E_USER_ERROR, E_USER_NOTICE]
//Now you can use the custom error handling function by using trigger_error

Practice questions:

The code is as follows

Copy code

代码如下

复制代码

date_default_timezone_set('PRC');
function myerror($error_level,$error_message){
$info= "错误号：$error_leveln";
$info.= "错误信息：$error_messagen";
$info.= '发生时间：'.date('Y-m-d H:i:s');
$filename='aa.txt';
if(!$fp=fopen($filename,'a')){
'创建文件'.$filename.'失败';
}
if(is_writeable($filename)){
if(!fwrite($fp,$info)){
echo '写入文件失败';
} else {
echo '已成功记录错误信息';
}
fclose($fp);
} else {
echo '文件'.$filename.'不可写';
}
exit();
}
set_error_handler('myerror',E_WARNING);
$fp=fopen('aaa.txt','r');
?>

date_default_timezone_set('PRC');

function myerror($error_level,$error_message){

$info= "Error number: $error_leveln";

} else {

echo 'File'.$filename.'Not writable'; }

exit();

} <🎜> set_error_handler('myerror',E_WARNING); <🎜> $fp=fopen('aaa.txt','r'); <🎜> ?>

1 2 http://www.bkjia.com/PHPjc/632215.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/632215.htmlTechArticleThe most commonly used error mechanism we use in php is try catch{}, which can be easily caught. Errors have been detected, but in php, error viewing and error closing are also provided for many...

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

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

How to fix KB5055612 fails to install in Windows 10?

4 weeks ago By DDD

Roblox: Bubble Gum Simulator Infinity - How To Get And Use Royal Keys

4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

Roblox: Grow A Garden - Complete Mutation Guide

3 weeks ago By DDD

Nordhold: Fusion System, Explained

4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

Mandragora: Whispers Of The Witch Tree - How To Unlock The Grappling Hook

3 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

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

Java Tutorial

1672

CakePHP Tutorial

1428

Laravel Tutorial

1332

PHP Tutorial

1276

C# Tutorial

1256

Related knowledge

PHP: A Key Language for Web Development Apr 13, 2025 am 12:08 AM

PHP is a scripting language widely used on the server side, especially suitable for web development. 1.PHP can embed HTML, process HTTP requests and responses, and supports a variety of databases. 2.PHP is used to generate dynamic web content, process form data, access databases, etc., with strong community support and open source resources. 3. PHP is an interpreted language, and the execution process includes lexical analysis, grammatical analysis, compilation and execution. 4.PHP can be combined with MySQL for advanced applications such as user registration systems. 5. When debugging PHP, you can use functions such as error_reporting() and var_dump(). 6. Optimize PHP code to use caching mechanisms, optimize database queries and use built-in functions. 7

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.

PHP in Action: Real-World Examples and Applications Apr 14, 2025 am 12:19 AM

PHP is widely used in e-commerce, content management systems and API development. 1) E-commerce: used for shopping cart function and payment processing. 2) Content management system: used for dynamic content generation and user management. 3) API development: used for RESTful API development and API security. Through performance optimization and best practices, the efficiency and maintainability of PHP applications are improved.

The Enduring Relevance of PHP: Is It Still Alive? Apr 14, 2025 am 12:12 AM

PHP is still dynamic and still occupies an important position in the field of modern programming. 1) PHP's simplicity and powerful community support make it widely used in web development; 2) Its flexibility and stability make it outstanding in handling web forms, database operations and file processing; 3) PHP is constantly evolving and optimizing, suitable for beginners and experienced developers.

PHP and Python: Different Paradigms Explained Apr 18, 2025 am 12:26 AM

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 vs. Other Languages: A Comparison Apr 13, 2025 am 12:19 AM

PHP is suitable for web development, especially in rapid development and processing dynamic content, but is not good at data science and enterprise-level applications. Compared with Python, PHP has more advantages in web development, but is not as good as Python in the field of data science; compared with Java, PHP performs worse in enterprise-level applications, but is more flexible in web development; compared with JavaScript, PHP is more concise in back-end development, but is not as good as JavaScript in front-end development.

PHP and Python: Code Examples and Comparison Apr 15, 2025 am 12:07 AM

PHP and Python have their own advantages and disadvantages, and the choice depends on project needs and personal preferences. 1.PHP is suitable for rapid development and maintenance of large-scale web applications. 2. Python dominates the field of data science and machine learning.

PHP: Handling Databases and Server-Side Logic Apr 15, 2025 am 12:15 AM

PHP uses MySQLi and PDO extensions to interact in database operations and server-side logic processing, and processes server-side logic through functions such as session management. 1) Use MySQLi or PDO to connect to the database and execute SQL queries. 2) Handle HTTP requests and user status through session management and other functions. 3) Use transactions to ensure the atomicity of database operations. 4) Prevent SQL injection, use exception handling and closing connections for debugging. 5) Optimize performance through indexing and cache, write highly readable code and perform error handling.

See all articles