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

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

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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:

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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:

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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:

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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:

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代码如下

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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";

$info.= "Error message: $error_messagen"; $info.= 'Occurrence time:'.date('Y-m-d H:i:s'); $filename='aa.txt'; if(!$fp=fopen($filename,'a')){ 'Create file'.$filename.'Failed'; } if(is_writeable($filename)){ if(!fwrite($fp,$info)){ echo 'Failed to write file'; } else { echo 'Error message recorded successfully'; } fclose($fp);

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

exit();

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

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