比较运算符
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
错误控制运算符
PHP 支持一个错误控制运算符：@。当将其放置在一个 PHP 表达式之前，该表达式可能产生的任何错误信息都被忽略掉。
如果激活了 track_errors 特性，表达式所产生的任何错误信息都被存放在变量 $php_errormsg 中。此变量在每次出错时都会被覆盖，所以如果想用它的话就要尽早检查。
<?php
/* Intentional file error */
$my_file = @file ('non_existent_file') or
die ("Failed opening file: error was '$php_errormsg'");
// this works for any expression, not just functions:
$value = @$cache[$key];
// will not issue a notice if the index $key doesn't exist.
?>
Note: @ 运算符只对表达式有效。对新手来说一个简单的规则就是：如果能从某处得到值，就能在它前面加上 @ 运算符。例如，可以把它放在变量，函数和 include() 调用，常量，等等之前。不能把它放在函数或类的定义之前，也不能用于条件结构例如 if 和 foreach 等。
参见 error_reporting() 及手册中错误处理及日志函数的有关章节。
Warning
目前的“@”错误控制运算符前缀甚至使导致脚本终止的严重错误的错误报告也失效。这意味着如果在某个不存在或类型错误的函数调用前用了“@”来抑制错误信息，那脚本会没有任何迹象显示原因而死在那里。
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User Contributed Notes错误控制运算符
taras dot dot dot di at gmail dot com
12-Aug-2008 11:29
12-Aug-2008 11:29
beatngu
27-May-2008 05:29
27-May-2008 05:29
NB The @ operator doesn't work when throwing errors as exceptions using the ErrorException class
nospam at blog dot fileville dot net
04-Jan-2007 03:58
04-Jan-2007 03:58
If you want to log all the error messages for a php script from a session you can use something like this:
<?php
session_start();
function error($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 09:52
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 09:38
13-Oct-2006 09:38
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
04-Mar-2005 12:25
04-Mar-2005 12:25
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
27-Dec-2004 12:19
27-Dec-2004 12:19
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.