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Оператор управления ошибками

PHP поддерживает один оператор управления ошибками: знак @. В случае, если он предшествует какому-либо выражению в PHP-коде, любые сообщения об ошибках, генерируемые этим выражением, будут проигнорированы.

В случае, если установлена опция track_errors, все генерируемые сообщения об ошибках будут сохраняться в переменной $php_errormsg. Эта переменная будет перезаписываться при возникновении каждой новой ошибки, поэтому в случае необходимости проверяйте ее сразу же.

<?php
// Преднамеренная ошибка при работе с файлами
$my_file = @file ('non_existent_file') or
    die (
"Failed opening file: error was '$php_errormsg'");

// работает для любых выражений, а не только для функций
$value = @$cache[$key]; 
// В случае если ключа $key нет, сообщение об ошибке не будет отображено

?>

Замечание: Оператор @ работает только с выражениями. Есть простое правило: если произвольная языковая конструкция возвращает значение, значит вы можете использовать предшествующий ей оператор @. Например, вы можете использовать @ перед именем переменной, произвольной функцией или вызовом include(), константой и так далее. В то же время вы не можете использовать этот оператор перед определением функции или класса, условными конструкциями, такими как if или foreach.

Также ознакомьтесь с описанием функции error_reporting() и соответствующим разделом документации Обработка ошибок и функции логирования.

Замечание: Оператор @ не подавляет вывод ошибок, возникающих на стадии синтаксического разбора скрипта.

Внимание

На сегодняшний день оператор @ подавляет вывод сообщений даже о критических ошибках прерывающих работу скрипта. Помимо всего прочего, это означает, что если вы использовали @ для подавления ошибок, возникающих при работе какой-либо функции, в случае если она недоступна или написана неправильно, дальнейшая работа скрипта будет остановлена без каких-либо уведомлений.


User Contributed Notes
Error Control Operators
M. T.
11-Oct-2009 04:20
Be aware of using error control operator in statements before include() like this:

<?PHP

(@include("file.php"))
 OR die(
"Could not find file.php!");

?>

This cause, that error reporting level is set to zero also for the included file. So if there are some errors in the included file, they will be not displayed.
dsbeam at gmail dot com
02-Sep-2009 02:22
Though error suppression can be dangerous at times, it can be useful as well.  I've found the following statements roughly equivalent:

     if( isset( $var ) && $var === $something )
     if( @$var === $something )

EXCEPT when you're comparing against a boolean value (when $something is false).  In that case, if it's not set the conditional will still be triggered.

I've found this useful when I want to check a value that might not exist:

     if( @$_SERVER[ 'HTTP_REFERER' ] !== '/www/some/path/file' )

or when we want to see if a checkbox / radio button have been submitted with a post action

     if( @$_POST[ 'checkbox' ] === 'yes' )

Just letting you guys know my findings, :)
gerrywastaken
19-May-2009 08:46
Error suppression should be avoided if possible as it doesn't just suppress the error that you are trying to stop, but will also suppress errors that you didn't predict would ever occur. This will make debugging a nightmare.

It is far better to test for the condition that you know will cause an error before preceding to run the code. This way only the error that you know about will be suppressed and not all future errors associated with that piece of code.

There may be a good reason for using outright error suppression in favor of the method I have suggested, however in the many years I've spent programming web apps I've yet to come across a situation where it was a good solution. The examples given on this manual page are certainly not situations where the error control operator should be used.
taras dot dot dot di at gmail dot com
12-Aug-2008 03:29
I was confused as to what the @ symbol actually does, and after a few experiments have concluded the following:

* the error handler that is set gets called regardless of what level the error reporting is set on, or whether the statement is preceeded with @

* it is up to the error handler to impart some meaning on the different error levels. You could make your custom error handler echo all errors, even if error reporting is set to NONE.

* so what does the @ operator do? It temporarily sets the error reporting level to 0 for that line. If that line triggers an error, the error handler will still be called, but it will be called with an error level of 0

Hope this helps someone
beatngu
27-May-2008 09:29
NB The @ operator doesn't work when throwing errors as exceptions using the ErrorException class
nospam at blog dot fileville dot net
03-Jan-2007 07:58
If you want to log all the error messages for a php script from a session you can use something like this:
<?php
 session_start
();
  function
error($error, $return=FALSE) {
      global
$php_errormsg;
      if(isset(
$_SESSION['php_errors'])) {
       
$_SESSION['php_errors'] = array();    
    }
 
$_SESSION['php_errors'][] = $error; // Maybe use $php_errormsg
 
if($return == TRUE) {
   
$message = "";
       foreach(
$_SESSION['php_errors'] as $php_error) {
         
$messages .= $php_error."\n";
     } 
    return
$messages; // Or you can use use $_SESSION['php_errors']
 
}
}
?>
Hope this helps someone...
13-Dec-2006 01:52
error_reporting()==0 for detecting the @ error suppression assumes that you did not set the error level to 0 in the first place.

However, typically if you want to set your own error handler, you would set the error_reporting to 0. Therefore, an alternative to detect the @ error suppression is required.
programming at kennebel dot com
13-Oct-2006 01:38
To suppress errors for a new class/object:

<?php
// Tested: PHP 5.1.2 ~ 2006-10-13

// Typical Example
$var = @some_function();

// Class/Object Example
$var = @new some_class();

// Does NOT Work!
//$var = new @some_class(); // syntax error
?>

I found this most useful when connecting to a
database, where i wanted to control the errors
and warnings displayed to the client, while still
using the class style of access.
me at hesterc dot fsnet dot co dot uk
03-Mar-2005 04:25
If you wish to display some text when an error occurs, echo doesn't work. Use print instead. This is explained on the following link 'What is the difference between echo and print?':

http://www.faqts.com/knowledge_base/view.phtml/aid/1/fid/40

It says "print can be used as part of a more complex expression where echo cannot".

Also, you can add multiple code to the result when an error occurs by separating each line with "and". Here is an example:

<?php
$my_file
= @file ('non_existent_file') or print 'File not found.' and $string = ' Honest!' and print $string and $fp = fopen ('error_log.txt', 'wb+') and fwrite($fp, $string) and fclose($fp);
?>

A shame you can't use curly brackets above to enclose multiple lines of code, like you can with an if statement or a loop. It could make for a single long line of code. You could always call a function instead.
frogger at netsurf dot de
26-Dec-2004 04:19
Better use the function trigger_error() (http://de.php.net/manual/en/function.trigger-error.php)
to display defined notices, warnings and errors than check the error level your self. this lets you write messages to logfiles if defined in the php.ini, output
messages in dependency to the error_reporting() level and suppress output using the @-sign.
 

 
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