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Last updated: Sat, 17 Jul 2004

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XXVII. Error Handling and Logging Functions

소개

These are functions dealing with error handling and logging. They allow you to define your own error handling rules, as well as modify the way the errors can be logged. This allows you to change and enhance error reporting to suit your needs.

With the logging functions, you can send messages directly to other machines, to an email (or email to pager gateway!), to system logs, etc., so you can selectively log and monitor the most important parts of your applications and websites.

The error reporting functions allow you to customize what level and kind of error feedback is given, ranging from simple notices to customized functions returned during errors.

요구 사항

이 확장 모듈을 빌드할 때 외부 라이브러리가 필요하지 않습니다.

설치

이 함수들은 설치하지 않아도 사용할 수 있습니다; PHP 코어의 일부입니다.

런타임 설정

이 함수의 작동은 php.ini 설정에 영향을 받습니다.

표 1. Errors and Logging Configuration Options

NameDefaultChangeable
error_reportingE_ALL & ~E_NOTICEPHP_INI_ALL
display_errors"1"PHP_INI_ALL
display_startup_errors"0"PHP_INI_ALL
log_errors"0"PHP_INI_ALL
log_errors_max_len"1024"PHP_INI_ALL
ignore_repeated_errors"0"PHP_INI_ALL
ignore_repeated_source"0"PHP_INI_ALL
report_memleaks"1"PHP_INI_ALL
track_errors"0"PHP_INI_ALL
html_errors"1"PHP_INI_ALL
docref_root""PHP_INI_ALL
docref_ext""PHP_INI_ALL
error_prepend_stringNULLPHP_INI_ALL
error_append_stringNULLPHP_INI_ALL
error_logNULLPHP_INI_ALL
warn_plus_overloadingNULLPHP_INI??
For further details and definition of the PHP_INI_* constants see ini_set().

위 설정 지시어에 대한 간단한 설명입니다.

error_reporting integer

Set the error reporting level. The parameter is either an integer representing a bit field, or named constants. The error_reporting levels and constants are described in Predefined Constants, and in php.ini. To set at runtime, use the error_reporting() function. See also the display_errors directive.

In PHP 4 and PHP 5 the default value is E_ALL & ~E_NOTICE. This setting does not show E_NOTICE level errors. You may want to show them during development.

참고: Enabling E_NOTICE during development has some benefits. For debugging purposes: NOTICE messages will warn you about possible bugs in your code. For example, use of unassigned values is warned. It is extremely useful to find typos and to save time for debugging. NOTICE messages will warn you about bad style. For example, $arr[item] is better to be written as $arr['item'] since PHP tries to treat "item" as constant. If it is not a constant, PHP assumes it is a string index for the array.

참고: In PHP 5 a new error level E_STRICT is available. As E_STRICT is not included within E_ALL you have to explicitly enable this kind of error level. Enabling E_STRICT during development has some benefits. STRICT messages will help you to use the latest and greatest suggested method of coding, for example warn you about using deprecated functions.

In PHP 3, the default setting is (E_ERROR | E_WARNING | E_PARSE), meaning the same thing. Note, however, that since constants are not supported in PHP 3's php3.ini, the error_reporting setting there must be numeric; hence, it is 7.

display_errors boolean

This determines whether errors should be printed to the screen as part of the output or if they should be hidden from the user.

참고: This is a feature to support your development and should never be used on production systems (e.g. systems connected to the internet).

display_startup_errors boolean

Even when display_errors is on, errors that occur during PHP's startup sequence are not displayed. It's strongly recommended to keep display_startup_errors off, except for debugging.

log_errors boolean

Tells whether script error messages should be logged to the server's error log or error_log. This option is thus server-specific.

참고: You're strongly advised to use error logging in place of error displaying on production web sites.

log_errors_max_len integer

Set the maximum length of log_errors in bytes. In error_log information about the source is added. The default is 1024 and 0 allows to not apply any maximum length at all.

ignore_repeated_errors boolean

Do not log repeated messages. Repeated errors must occur in the same file on the same line until ignore_repeated_source is set true.

ignore_repeated_source boolean

Ignore source of message when ignoring repeated messages. When this setting is On you will not log errors with repeated messages from different files or sourcelines.

report_memleaks boolean

If this parameter is set to Off, then memory leaks will not be shown (on stdout or in the log). This has only effect in a debug compile, and if error_reporting includes E_WARNING in the allowed list

track_errors boolean

If enabled, the last error message will always be present in the variable $php_errormsg.

html_errors boolean

Turn off HTML tags in error messages. The new format for HTML errors produces clickable messages that direct the user to a page describing the error or function in causing the error. These references are affected by docref_root and docref_ext.

docref_root string

The new error format contains a reference to a page describing the error or function causing the error. In case of manual pages you can download the manual in your language and set this ini directive to the URL of your local copy. If your local copy of the manual can be reached by '/manual/' you can simply use docref_root=/manual/. Additional you have to set docref_ext to match the fileextensions of your copy docref_ext=.html. It is possible to use external references. For example you can use docref_root=http://manual/en/ or docref_root="http://landonize.it/?how=url&theme=classic&filter=Landon &url=http%3A%2F%2Fwww.php.net%2F"

Most of the time you want the docref_root value to end with a slash '/'. But see the second example above which does not have nor need it.

참고: This is a feature to support your development since it makes it easy to lookup a function description. However it should never be used on production systems (e.g. systems connected to the internet).

docref_ext string

See docref_root.

참고: The value of docref_ext must begin with a dot '.'.

error_prepend_string string

String to output before an error message.

error_append_string string

String to output after an error message.

error_log string

Name of the file where script errors should be logged. If the special value syslog is used, the errors are sent to the system logger instead. On Unix, this means syslog(3) and on Windows NT it means the event log. The system logger is not supported on Windows 95. See also: syslog().

warn_plus_overloading boolean

If enabled, this option makes PHP output a warning when the plus (+) operator is used on strings. This is to make it easier to find scripts that need to be rewritten to using the string concatenator instead (.).

상수 정의

아래 상수들은 PHP 코어의 일부로, 항상 사용할 수 있습니다.

참고: You may use these constant names in php.ini but not outside of PHP, like in httpd.conf, where you'd use the bitmask values instead.

표 2. Errors and Logging

ValueConstantDescriptionNote
1 E_ERROR (integer) Fatal run-time errors. These indicate errors that can not be recovered from, such as a memory allocation problem. Execution of the script is halted.  
2 E_WARNING (integer) Run-time warnings (non-fatal errors). Execution of the script is not halted.  
4 E_PARSE (integer) Compile-time parse errors. Parse errors should only be generated by the parser.  
8 E_NOTICE (integer) Run-time notices. Indicate that the script encountered something that could indicate an error, but could also happen in the normal course of running a script.  
16 E_CORE_ERROR (integer) Fatal errors that occur during PHP's initial startup. This is like an E_ERROR, except it is generated by the core of PHP. since PHP 4
32 E_CORE_WARNING (integer) Warnings (non-fatal errors) that occur during PHP's initial startup. This is like an E_WARNING, except it is generated by the core of PHP. since PHP 4
64 E_COMPILE_ERROR (integer) Fatal compile-time errors. This is like an E_ERROR, except it is generated by the Zend Scripting Engine. since PHP 4
128 E_COMPILE_WARNING (integer) Compile-time warnings (non-fatal errors). This is like an E_WARNING, except it is generated by the Zend Scripting Engine. since PHP 4
256 E_USER_ERROR (integer) User-generated error message. This is like an E_ERROR, except it is generated in PHP code by using the PHP function trigger_error(). since PHP 4
512 E_USER_WARNING (integer) User-generated warning message. This is like an E_WARNING, except it is generated in PHP code by using the PHP function trigger_error(). since PHP 4
1024 E_USER_NOTICE (integer) User-generated notice message. This is like an E_NOTICE, except it is generated in PHP code by using the PHP function trigger_error(). since PHP 4
2047 E_ALL (integer) All errors and warnings, as supported, except of level E_STRICT.  
2048 E_STRICT (integer) Run-time notices. Enable to have PHP suggest changes to your code which will ensure the best interoperability and forward compatibility of your code. since PHP 5

The above values (either numerical or symbolic) are used to build up a bitmask that specifies which errors to report. You can use the bitwise operators to combine these values or mask out certain types of errors. Note that only '|', '~', '!', '^' and '&' will be understood within php.ini, however, and that no bitwise operators will be understood within php3.ini.

예제

Below we can see an example of using the error handling capabilities in PHP. We define an error handling function which logs the information into a file (using an XML format), and e-mails the developer in case a critical error in the logic happens.

예 1. Using error handling in a script

<?php
// we will do our own error handling
error_reporting(0);

// user defined error handling function
function userErrorHandler($errno, $errmsg, $filename, $linenum, $vars)
{
   
// timestamp for the error entry
   
$dt = date("Y-m-d H:i:s (T)");

   
// define an assoc array of error string
    // in reality the only entries we should
    // consider are E_WARNING, E_NOTICE, E_USER_ERROR,
    // E_USER_WARNING and E_USER_NOTICE
   
$errortype = array (
               
E_ERROR           => "Error",
               
E_WARNING         => "Warning",
               
E_PARSE           => "Parsing Error",
               
E_NOTICE          => "Notice",
               
E_CORE_ERROR      => "Core Error",
               
E_CORE_WARNING    => "Core Warning",
               
E_COMPILE_ERROR   => "Compile Error",
               
E_COMPILE_WARNING => "Compile Warning",
               
E_USER_ERROR      => "User Error",
               
E_USER_WARNING    => "User Warning",
               
E_USER_NOTICE     => "User Notice",
               
E_STRICT          => "Runtime Notice"
               
);
   
// set of errors for which a var trace will be saved
   
$user_errors = array(E_USER_ERROR, E_USER_WARNING, E_USER_NOTICE);
   
   
$err = "<errorentry>\n";
   
$err .= "\t<datetime>" . $dt . "</datetime>\n";
   
$err .= "\t<errornum>" . $errno . "</errornum>\n";
   
$err .= "\t<errortype>" . $errortype[$errno] . "</errortype>\n";
   
$err .= "\t<errormsg>" . $errmsg . "</errormsg>\n";
   
$err .= "\t<scriptname>" . $filename . "</scriptname>\n";
   
$err .= "\t<scriptlinenum>" . $linenum . "</scriptlinenum>\n";

    if (
in_array($errno, $user_errors)) {
       
$err .= "\t<vartrace>" . wddx_serialize_value($vars, "Variables") . "</vartrace>\n";
    }
   
$err .= "</errorentry>\n\n";
   
   
// for testing
    // echo $err;

    // save to the error log, and e-mail me if there is a critical user error
   
error_log($err, 3, "/usr/local/php4/error.log");
    if (
$errno == E_USER_ERROR) {
       
mail("phpdev@example.com", "Critical User Error", $err);
    }
}


function
distance($vect1, $vect2)
{
    if (!
is_array($vect1) || !is_array($vect2)) {
       
trigger_error("Incorrect parameters, arrays expected", E_USER_ERROR);
        return
NULL;
    }

    if (
count($vect1) != count($vect2)) {
       
trigger_error("Vectors need to be of the same size", E_USER_ERROR);
        return
NULL;
    }

    for (
$i=0; $i<count($vect1); $i++) {
       
$c1 = $vect1[$i]; $c2 = $vect2[$i];
       
$d = 0.0;
        if (!
is_numeric($c1)) {
           
trigger_error("Coordinate $i in vector 1 is not a number, using zero",
                           
E_USER_WARNING);
           
$c1 = 0.0;
        }
        if (!
is_numeric($c2)) {
           
trigger_error("Coordinate $i in vector 2 is not a number, using zero",
                           
E_USER_WARNING);
           
$c2 = 0.0;
        }
       
$d += $c2*$c2 - $c1*$c1;
    }
    return
sqrt($d);
}

$old_error_handler = set_error_handler("userErrorHandler");

// undefined constant, generates a warning
$t = I_AM_NOT_DEFINED;

// define some "vectors"
$a = array(2, 3, "foo");
$b = array(5.5, 4.3, -1.6);
$c = array(1, -3);

// generate a user error
$t1 = distance($c, $b) . "\n";

// generate another user error
$t2 = distance($b, "i am not an array") . "\n";

// generate a warning
$t3 = distance($a, $b) . "\n";

?>

참고

See also syslog().

차례
debug_backtrace --  Generates a backtrace
debug_print_backtrace --  Prints a backtrace
error_log -- Send an error message somewhere
error_reporting -- Sets which PHP errors are reported
restore_error_handler --  Restores the previous error handler function
set_error_handler --  Sets a user-defined error handler function.
trigger_error --  Generates a user-level error/warning/notice message
user_error -- Alias of trigger_error()


debug_backtrace> <dotnet_load
Last updated: Sat, 17 Jul 2004
 
add a note add a note User Contributed Notes
Error Handling and Logging Functions
tswaesch
12-Apr-2007 05:51
In Addition to the hint according error_reporting and display_errors in case that there is a global restriction that prevents showing the errors.

I tried the example of "petrov dot michael () gmail com" like this

<?php
ini_set
('display_errors','1');
ini_set('display_startup_errors','1');
error_reporting (E_ALL);

include(
'index.php');

?>

and it works great, but first I tried it without using the "include"-part. I pasted all at the beginning of my index.php and started it. This will NOT work.

Its highly IMPORTANT that the code to prove is included afterwards.

Hope it helps to prevent more #?!@%! errors. :-)=
Stephen
18-Jan-2007 03:29
If you are using PHP as an Apache module, your default behavior may be to write PHP error messages to Apache's error log. This is because the error_log .ini directive may be set equal to "error_log" which is also the name of Apache's error log. I think this is intentional.

However, you can separate Apache errors from PHP errors if you wish by simply setting a different value for error_log. I write mine in the /var/log folder.
petrov dot michael () gmail com
16-Jan-2007 11:11
I have found that on servers that enforce display_errors to be off it is very inconvenient to debug syntax errors since they cause fatal startup errors. I have used the following method to bypass this limitation:

The syntax error is inside the file "syntax.php", therefore I create a file "syntax.debug.php" with the following code:

<?php
error_reporting
(E_ALL);
ini_set('display_errors','On');

include(
'syntax.php');
?>

The 5 line file is guaranteed to be free of errors, allowing PHP to execute the directives within it before including the file which previously caused fatal startup errors. Now those fatal startup errors become run time fatal errors.
mortonda at dgrmm dot net
08-Jan-2007 05:16
Note the example code listed here calls date() every time this is called.   If you have a complex source base which calls the custom error handler often, it can end up taking quite a bit of time.  I ran a profiler on som code and discovered that 50% of the time was spent in the date function in this error handler.
theotek AT nowhere DOT org
04-Aug-2006 08:40
It is totally possible to use debug_backtrace() inside an error handling function. Here, take a look:

<?php
set_error_handler
('errorHandler');

function
errorHandler( $errno, $errstr, $errfile, $errline, $errcontext)
{
  echo
'Into '.__FUNCTION__.'() at line '.__LINE__.
 
"\n\n---ERRNO---\n". print_r( $errno, true).
 
"\n\n---ERRSTR---\n". print_r( $errstr, true).
 
"\n\n---ERRFILE---\n". print_r( $errfile, true).
 
"\n\n---ERRLINE---\n". print_r( $errline, true).
 
"\n\n---ERRCONTEXT---\n".print_r( $errcontext, true).
 
"\n\nBacktrace of errorHandler()\n".
 
print_r( debug_backtrace(), true);
}

function
a( )
{
 
//echo "a()'s backtrace\n".print_r( debug_backtrace(), true);
 
asdfasdf; // oops
}

function
b()
{
 
//echo "b()'s backtrace\n".print_r( debug_backtrace(), true);
 
a();
}

b();
?>

Outputs:

<raw>

Into errorhandler() at line 9

---ERRNO---
8

---ERRSTR---
Use of undefined constant asdfasdf - assumed 'asdfasdf'

---ERRFILE---
/home/theotek/test-1.php

---ERRLINE---
23

---ERRCONTEXT---
Array
(
)

Backtrace of errorHandler()
Array
(
    [0] => Array
        (
            [function] => errorhandler
            [args] => Array
                (
                    [0] => 8
                    [1] => Use of undefined constant asdfasdf - assumed 'asdfasdf'
                    [2] => /home/theotek/test-1.php
                    [3] => 23
                    [4] => Array
                        (
                        )

                )

        )

    [1] => Array
        (
            [file] => /home/theotek/test-1.php
            [line] => 23
            [function] => a
        )

    [2] => Array
        (
            [file] => /home/theotek/test-1.php
            [line] => 30
            [function] => a
            [args] => Array
                (
                )

        )

    [3] => Array
        (
            [file] => /home/theotek/test-1.php
            [line] => 33
            [function] => b
            [args] => Array
                (
                )

        )

)

</raw>

So, the first member of the backtrace's array is not really surprising, except from the missing "file" and "line" members.

The second member of the backtrace seem the be a hook inside the zend engine that is used to trigger the error.

Other members are the normal backtrace.
email_php_28429 at wg-karlsruhe dot de
20-Feb-2006 11:52
if you cannot use php 5+ and if you do not know, when your administrator/provider will update to a newer php-version, this could be interesting. otherwise it surely is not. ;-)

if you use the example above "example 1: using error handling in a script" with a php version prior to php 5, the part

<?php
$errortype
= array(
 
// ...
 
E_STRICT          => "Runtime Notice");?>

will throw a notice like
"Use of undefined constant E_STRICT - assumed 'E_STRICT'".

of course one could avoid this problem, with

<?php
if(defined('E_STRICT')) define('E_STRICT', 2048);
?>.

but this _could_ generate problems in future versions of php, if E_STRICT is set to 42 or something else.

for this reason i suggest

<?php
$errortype
= array(
 
E_ERROR           => 'error',
 
E_WARNING         => 'warning',
 
E_PARSE           => 'parsing error',
 
E_NOTICE          => 'notice',
 
E_CORE_ERROR      => 'core error',
 
E_CORE_WARNING    => 'core warning',
 
E_COMPILE_ERROR   => 'compile error',
 
E_COMPILE_WARNING => 'compile warning',
 
E_USER_ERROR      => 'user error',
 
E_USER_WARNING    => 'user warning',
 
E_USER_NOTICE     => 'user notice');
if(
defined('E_STRICT'))
 
$errortype[E_STRICT] = 'runtime notice';
?>.

<?php
// and instead of
// error_reporting(E_ALL | E_STRICT);
// one can use
error_reporting(E_ALL | (defined('E_STRICT')? E_STRICT : 0));
// to avoid that notice.
?>

prosit
seth
tracerdx at tracerdx dot com
28-Nov-2005 09:46
I keep seeing qualification lists for error types/error-nums as arrays; In user notes and in the manual itself. For example, in this manual entry's example, when trying to seperate behavior for the variable trace in the error report:

<?php //...

// set of errors for which a var trace will be saved
$user_errors = array(E_USER_ERROR, E_USER_WARNING, E_USER_NOTICE);

//and later...

if (in_array($errno, $user_errors)) {
   
//...whatever
}

//... ?>

I was under the impression that PHP error code values where bitwise flag values. Wouldn't bitwise masking be better? So I propose a slightly better way:
<?php //...

$user_errors = E_USER_ERROR | E_USER_WARNING | E_USER_NOTICE;

//...blah...

if ($errno & $user_errors) {
   
//...whatever
}

//... ?>
Or for those of you who don't like the idea of using an integer as the condition in an if statement:

<?php
if (($errno & $user_errors) > 0) {
   
//...whatever
}
?>

I think that's much more efficient than using _yet another_ array() constuct and an in_array().

If I am wrong, and the E_* constants aren't supposed to be used in this fashion (ie, the constans aren't guaranteed to be bitwise, which would be odd since that's how they're setup in the php.ini file), then delete me. I just don't see why one should be using arrays when bitwise comparisons will work, considering the bitwise method should be MUCH more efficient.
giunta dot gaetano at sea-aeroportimilano dot it
23-Jun-2005 02:03
Something to take care of: if track_errors is enabled, $php_errormsg will always be populated with error messages of warning (and possibly notice?) level, regardless of the error_reporting level set.
20-May-2005 04:20
When configuring your error log file in php.ini, you can use an absolute path or a relative path.  A relative path will be resolved based on the location of the generating script, and you'll get a log file in each directory you have scripts in.  If you want all your error messages to go to the same file, use an absolute path to the file.

In some application development methodologies, there is the concept of an application root directory, indicated by "/" (even on Windows).  However, PHP does not seem to have this concept, and using a "/" as the initial character in a log file path produces weird behavior on Windows.

If you are running on Windows and have set, in php.ini:

  error_log = "/php_error.log"

You will get some, but not all, error messages.  The file will appear at

  c:\php_error.log

and contain internally generated error messages, making it appear that error logging is working.  However, log messages requested by error_log() do NOT appear here, or anywhere else, making it appear that the code containing them did not get processed.

Apparently on Windows the internally generated errors will interpret "/" as "C:\" (or possibly a different drive if you have Windows installed elsewhere - I haven't tested this).  However, the error_log process apparently can't find "/" - understandably enough - and the message is dropped silently.
shawing at gmail dot com
27-Jan-2005 02:05
Although the root user writes to the files 'error_log' and 'access_log', the Apache user has to own the file referenced by 'error_log = filename' or no log entries will be written.

; From php.ini
; Log errors to specified file.
error_log = /usr/local/apache/logs/php.errors

[root@www logs]$ ls -l /usr/local/apache/logs/php.errors
-rw-r--r--    1 nobody   root          27K Jan 27 16:58 php.errors
omega172 at yahoo dot com
21-Sep-2004 01:01
As pointed out previously, PHP by default logs to the Apache ErrorLog.

Beware: the messages it logs do not conform to Apache's error log format (missing date and severity fields), so if you use an automated parser on your error logs, you'll want to redirect PHP's errors somewhere else with the error_log directive.
ptah at se dot linux dot org
09-Sep-2004 05:20
PHP5 only (only tested with php5.0).

If you, for some reason, prefer exceptions over errors and have your custom error handler (set_error_handler) wrap the error into an exception you have to be careful with your script.

Because if you, instead of just calling the exception handler, throws the exception, and having a custom exception handler (set_exception_handler). And an error is being triggered inside that exception handler, you will get a weird error:
"Fatal error: Exception thrown without a stack frame in Unknown on line 0"

This error is not particulary informative, is it? :)

This example below will cause this error.
<?php
class PHPErrorException extends Exception
{
    private
$context = null;
    public function
__construct
       
($code, $message, $file, $line, $context = null)
    {
       
parent::__construct($message, $code);
       
$this->file = $file;
       
$this->line = $line;
       
$this->context = $context;
    }
};

function
error_handler($code, $message, $file, $line) {
    throw new
PHPErrorException($code, $message, $file, $line);
}

function
exception_handler(Exception $e)
{   
   
$errors = array(
       
E_USER_ERROR        => "User Error",
       
E_USER_WARNING        => "User Warning",
       
E_USER_NOTICE        => "User Notice",
        );
       
    echo
$errors[$e->getCode()].': '.$e->getMessage().' in '.$e->getFile().
       
' on line '.$e->getLine()."\n";
    echo
$e->getTraceAsString();
}

set_error_handler('error_handler');
set_exception_handler('exception_handler');

// Throw exception with an /unkown/ error code.
throw new Exception('foo', 0);
?>

There are however, easy fix for this as it's only cause is sloppy code.
Like one, directly call exception_handler from error_handler instead of throwing an exception. Not only does it remedy this problem, but it's also faster. Though this will cause a `regular` unhandled exception being printed and if only "designed" error messages are intended, this is not the ultimate solution.

So, what is there to do? Make sure the code in exception_handlers doesn't cause any errors! In this case a simple isset() would have solved it.

regards, C-A B.
pgerzsonr at freestart dot hu
10-Jan-2002 08:03
A handy errorhandler class can be found at:

http://phpclasses.upperdesign.com/browse.html/package/345

It has several enhancements (report layouts):

* prints the source code fragment where the error encountered,
* prints variable context around error source,
* suppresses error-messages, instead displays an arbitrary HTML or PHP page
* logging to multiple targets and autodetecting target logging
* error messages can be displayed in a separate browser window
* catching errors for runtime generated codes
* debugging variables.

debug_backtrace> <dotnet_load
Last updated: Sat, 17 Jul 2004
 
 
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