error handling in PHP

Hello


Motivation
The default error handling in PHP is very simple. An error message with filename, line number and a message describing the error is sent to the browser. 
What if you want to save this error also to a log file ? or catch warning\error\exception ?

Creating Custom Error Handler

Creating a custom error handler is quite simple. We simply create a special function that can be called when an error occurs in PHP.

This function must be able to handle a minimum of two parameters (error level and error message) but can accept up to five parameters (optionally: file, line-number, and the error context):

Syntax

error_function(error_level,error_message,
error_file,error_line,error_context)

Parameter	Description
error_level	Required. Specifies the error report level for the user-defined error. Must be a value number. See table below for possible error report levels
error_message	Required. Specifies the error message for the user-defined error
error_file	Optional. Specifies the filename in which the error occurred
error_line	Optional. Specifies the line number in which the error occurred
error_context	Optional. Specifies an array containing every variable, and their values, in use when the error occurred

Error Report levels

These error report levels are the different types of error the user-defined error handler can be used for:

Value	Constant	Description
2	E_WARNING	Non-fatal run-time errors. Execution of the script is not halted
8	E_NOTICE	Run-time notices. The script found something that might be an error, but could also happen when running a script normally
256	E_USER_ERROR	Fatal user-generated error. This is like an E_ERROR set by the programmer using the PHP function trigger_error()
512	E_USER_WARNING	Non-fatal user-generated warning. This is like an E_WARNING set by the programmer using the PHP function trigger_error()
1024	E_USER_NOTICE	User-generated notice. This is like an E_NOTICE set by the programmer using the PHP function trigger_error()
4096	E_RECOVERABLE_ERROR	Catchable fatal error. This is like an E_ERROR but can be caught by a user defined handle (see also set_error_handler())
8191	E_ALL	All errors and warnings (E_STRICT became a part of E_ALL in PHP 5.4)

Now lets create a function to handle errors: 

function customError($errno, $errstr) {
  echo "<b>Error:</b> [$errno] $errstr<br>";
  echo "Ending Script";
  die();
}

The code above is a simple error handling function. When it is triggered, it gets the error level and an error message. It then outputs the error level and message and terminates the script.

Now that we have created an error handling function we need to decide when it should be triggered.

Set Error Handler

function customError($errno, $errstr,$error_file,$error_line) 

{

    echo "<b>Error:</b> $error_file $error_line  [$errno] $errstr";

}

//set error handler

set_error_handler("customError");

//trigger error

echo($test);

this output :

Error: E:\nathan\PHP\VS\PHPWebProject2\PHPWebProject2\index.php 17 [8] Undefined variable: test

Using log file \ Email

you can send the error to a log_file using error_log

The error_log() function sends an error message to a log, to a file, or to a mail account.

---

error_log(message,type,destination,headers);

Parameter	Description
message	Required. Specifies the error message to log
type	Optional. Specifies where the error message should go. Possible values: 0 - Default. Message is sent to PHP's system logger, using the OS' system logging mechanism or a file, depending on what the error_log configuration is set to in php.ini 1 - Message is sent by email to the address in the destination parameter 2 - No longer in use (only available in PHP 3) 3 - Message is appended to the file specified in destination 4 - Message is sent directly to the SAPI logging handler
destination	Optional. Specifies the destination of the error message. This value depends on the value of thetype parameter
headers	Optional. Only used if the type parameter is set to 1. Specifies additional headers, like From, Cc, and Bcc. Multiple headers should be separated with a CRLF (\r\n)

function customError($errno, $errstr,$error_file,$error_line) 

{

    // --- error to display

    echo "<b>Error:</b>  [$errno] $errstr";

    // --- error to PHP system log

    $error = $error_file." ".$error_line." [".$errno."] ". $errstr;

    error_log($error,0); // send to php error file

   error_log($error,1,"natankrasney@gmail.com","From: webmaster@example.com");

}

//set error handler

set_error_handler("customError");

//trigger error

echo($test);

this will output to the browser :

and to the php error file (pending php.ini)

Exception Handling

the set_exception_handler() function sets a user-defined function to handle all uncaught exceptions.

<?php
function myException($exception) {
  echo "<b>Exception:</b> " . $exception->getMessage();
}

set_exception_handler('myException');

throw new Exception('Uncaught Exception occurred');
?>

The output of the code above should be something like this:

Exception: Uncaught Exception occurred

it is possible to log the exception as follows :

function customError($errno, $errstr,$error_file,$error_line)
{
    // --- error to display
    echo "<b>Error:</b>  [$errno] $errstr";
    // --- error to PHP system log
    $error = $error_file." ".$error_line." [".$errno."] ". $errstr;
    // send to php error file
    error_log($error,0); // send to php error file
    // send to php error to e-mail but need configuration
    //error_log($error,1,"natankrasney@gmail.com","From: webmaster@example.com");
}


function exception_handler($exception) {
    trigger_error( "Uncaught exception: ".$exception->getMessage()."\n");
}

set_exception_handler('exception_handler');


//set error handler
set_error_handler("customError");

$error = 'Always throw this error';
throw new Exception($error);

//trigger error
echo($test);



References

• http://www.w3schools.com/php/php_error.asp

Nathan

Using Logs in PHP - Log4PHP

Hello

Logging is a must for development and production enviroments.
Log4PHP is a logger for php (log4net exist for .net , log4j for java , .....)

download the sources from https://logging.apache.org/log4php/download.html
install src/main/php into your project. 


Sample code 1

1. include('log4php/Logger.php');
2. $logger = Logger::getLogger("main");
3. $logger->info("This is an informational message.");
4. $logger->warn("I'm not feeling so good...");

remark : here i copy it to a folder name Log4php

this result in :

Sample code 2

First, create a configuration file named config.xml containing:

<configuration xmlns="http://logging.apache.org/log4php/">
    <appender name="myAppender" class="LoggerAppenderFile">
        <param name="file" value="myLog.log" />
    </appender>
    <root>
        <level value="WARN" />
        <appender_ref ref="myAppender" />
    </root>
</configuration>

This configuration file does the following:

• line 2: Creates an appender named myAppender using appender class LoggerAppenderFile which is used for logging to a file.
• line 3: Sets the file parameter, which tells the appender to which file to write.
• line 6: Sets the root logger level to WARN. This means that logging requests with the level lower thanWARN will not be logged by the root logger.
• line 7: Links myAppender to the root logger so that all events recieved by the root logger will be forwarded to myAppender and written into the log file.
• 
  

Put this file at the same directory as your PHP project

To try it out, run the following code:

// Insert the path where you unpacked log4php
include('log4php/Logger.php');
 
// Tell log4php to use our configuration file.
Logger::configure('config.xml');
 
// Fetch a logger, it will inherit settings from the root logger
$log = Logger::getLogger('myLogger');
 
// Start logging
$log->trace("My first message.");   // Not logged because TRACE < WARN
$log->debug("My second message.");  // Not logged because DEBUG < WARN
$log->info("My third message.");    // Not logged because INFO < WARN
$log->warn("My fourth message.");   // Logged because WARN >= WARN
$log->error("My fifth message.");   // Logged because ERROR >= WARN
$log->fatal("My sixth message.");   // Logged because FATAL >= WARN

This result in myLog.log created as follows :

Sample code 3

This example covers named loggers, layouts and best practices in object-oriented programming.

Create a configuration file named config.xml with the following content:

<configuration xmlns="http://logging.apache.org/log4php/">
 
    <appender name="myConsoleAppender" class="LoggerAppenderConsole" />
    
    <appender name="myFileAppender" class="LoggerAppenderFile">
        <layout class="LoggerLayoutPattern">
            <param name="conversionPattern" value="%date [%logger] %message%newline" />
        </layout>
        <param name="file" value="myLog.log" />
    </appender>
 
    <logger name="Foo">
        <appender_ref ref="myFileAppender" />
    </logger>
    
    <root>
        <level value="DEBUG" />
        <appender_ref ref="myConsoleAppender" />
    </root>
</configuration>

The configuration defines two appenders: one writes to the console, and the other to a file.

The console appender doesn't have a layout defined, so it will revert to default layout (LoggerLayoutSimple). The file appender uses a different layout (LoggerLayoutPattern) which will result in different formatting of the logging events.

The console appender is linked to the root logger. The file appender is linked to the logger named Foo, however Foo also inherits appenders from the root logger (in this case the console appender). This means that logging events sent to the Foo logger will be logged both to the console and the file.

Consider the following code snippet:

// Include and configure log4php
include('log4php/Logger.php');
Logger::configure('config.xml');
 
/**
 * This is a classic usage pattern: one logger object per class.
 */
class Foo
{
    /** Holds the Logger. */
    private $log;
 
    /** Logger is instantiated in the constructor. */
    public function __construct()
    {
        // The __CLASS__ constant holds the class name, in our case "Foo".
        // Therefore this creates a logger named "Foo" (which we configured in the config file)
        $this->log = Logger::getLogger(__CLASS__);
    }
 
    /** Logger can be used from any member method. */
    public function go()
    {
        $this->log->info("We have liftoff.");
    }
}
 
$foo = new Foo();
$foo->go();

The output to file is as follows :

code for sample code 3 

Sample code 4

use rolling file with file name and line number
this appender fills the first file until maxFileSize [MB] then it copy the file to <file_name>1, after the second time it is to  <file_name>2 and this is maxBackupIndex times. after this the file is copy to  <file_name>1 and it start over again

Config.xml
<configuration xmlns="http://logging.apache.org/log4php/">
  <appender name="myAppenderRollingFile" class="LoggerAppenderRollingFile">
        <layout class="LoggerLayoutPattern">
            <param name="conversionPattern" value="%date %file : %line [%logger] %message%newline" />
        </layout>
        <param name="file" value="E:\wamp\www\TryLogger4PHP\file.log" />
        <param name="maxFileSize" value="1MB" />
        <param name="maxBackupIndex" value="5" />
    </appender>
 
<root>
        <level value="ERROR" />
        <appender_ref ref="myAppenderRollingFile" />
    </root>

  </configuration>

remarks

• one must use full path for file due to Log4PHP bug
• maxFileSize - max size of file
• maxBackupIndex - number of backup file

php file
<?php
// Include and configure log4php
include('log4php/Logger.php');


// Tell log4php to use our configuration file.

Logger::configure('config.xml');

// Fetch a logger, it will inherit settings from the root logger

$log = Logger::getLogger('myLogger');


// Start logging

$log->trace("My first message.");   // Not logged because TRACE < WARN

$log->debug("My second message.");  // Not logged because DEBUG < WARN

$log->info("My third message.");    // Not logged because INFO < WARN

$log->warn("My fourth message.");   // Logged because WARN >= WARN

$log->error("My fifth message.");   // Logged because ERROR >= WARN

$log->fatal("My sixth message.");   // Logged because FATAL >= WARN

?>

output :

code for sample code 4




References :

• https://logging.apache.org/log4php/

Nathan

ASP.Net - Logging

Hello


Log4net

The Basics

Three parts : configuration , setup , call

Configuration - done via app.config (desktop application) or web.config (web application)

Setup - set up and instantiate connection with Log4Net

Call - write to log

Logging Levels

There are 7 logs level  arranged from the highest priority at the top

1. OFF - nothing gets logged (cannot be called)
2. FATAL
3. ERROR
4. WARN
5. INFO
6. DEBUG
7. ALL - everything gets logged (cannot be called)

The Configuration

Root

You must have one root section.

It house the minimal level for all logger. 

All logger inherit it

<root>
  <level value="INFO"/>
  <appender-ref ref="FileAppender"/>
  <appender-ref ref="TraceAppender" />
</root>

Additional Loggers

Sometimes you will want to know more about a particular part of your application. log4net anticipated this by allowing you to specify additional logger references beyond just the root logger. For example, here is an additional logger that I have placed in our config file to log to the output messages that occur inside the OtherClass class object:

<logger name="Log4NetTest.OtherClass">
  <level value="DEBUG"/>
  <appender-ref ref="TraceAppender"/>
</logger>

Note that the logger name is the full name of the class including the namespace. If you wanted to monitor an entire namespace, it would be as simple as listing just the namespace you wanted to monitor. I would recommend against trying to re-use appenders in multiple loggers. It can be done, but you can get some unpredictable results.

In a config file where there will (potentially) be more information stored beyond just the log4net configuration information, you will need to specify a section to identify where the log4net configuration is housed. Here is a sample section that specifies that the configuration information will be stored under the XML tag "log4net":

<configSections>
  <section name="log4net" 
    type="log4net.Config.Log4NetConfigurationSectionHandler, log4net"/>
</configSections>

Appender (General)

An appender is the name for what logs the information. It specifies where the information will be logged, how it will be logged, and under what circumstances the information will be logged. While each appender has different parameters based upon where the data will be going, there are some common elements. The first is the name and type of the appender. Each appender must be named (anything you want) and have a type assigned to it (specific to the type of appender desired). Here is an example of an appender entry:

<appender name="TraceAppender" type="log4net.Appender.Trace
Appender">

Layout

Inside of each appender must be a layout section. This may be a bit different depending on the type of appender being used, but the basics are the same. You need a type that specifies how the data will be written. There are multiple options, but the one that I suggest you use is the pattern layout type. This will allow you to specify how you want your data written to the data repository. If you specify the pattern layout type, you will need a sub-tag that specifies a conversion pattern. This is the pattern by which your data should be written to the data repository. I will give a more detailed description of your options for the conversion patterns, but for now, here is an example of the layout tag with the pattern layout specified:

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<layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date [%thread] %-5level %logger [%ndc] 
    - %message%newline"/>
    </layout>

Conversion Patterns

See http://www.codeproject.com/Articles/140911/log4net-Tutorial

Filters

See http://www.codeproject.com/Articles/140911/log4net-Tutorial

Appenders

Each type of appender has its own set of syntax based upon where the data is going. The most unusual ones are the ones that log to databases. I will list a few of the ones that I think are most common. However, given the above information, you should be able to use the examples given online without any problems. The log4net site has some great examples of the different appenders. As I have said before, I used the log4net documentation extensively and this area was no exception. I usually copy their example and then modify it for my own purposes.

Trace Appender

It writes to the output window. This particular filter outputs a value like "2010-12-26 15:41:03,581 [10] WARN Log4NetTest.frmMain - This is a WARN test." It will include a new line at the end.

<appender name="TraceAppender" type="log4net.Appender.TraceAppender">  <layout type="log4net.Layout.PatternLayout">
    <conversionPattern value="%date{ABSOLUTE} 
    [%thread] %level %logger - %message%newline"/>
  </layout>
  <filter type="log4net.Filter.StringMatchFilter">
    <stringToMatch value="test" />
  </filter>
  <filter type="log4net.Filter.DenyAllFilter" />
</appender>

File Appender

This appender will write to a text file. The big differences to note here are that we have to specify the name of the text file (in this case, it is a file named mylogfile.txt that will be stored in the same location as the executable), we have specified that we should append to the file (instead of overwriting it), and we have specified that the FileAppender should use the Minimal Lock which will make the file usable by multiple appenders.

<appender name="FileAppender" type="log4net.Appender.FileAppender">
  <file value="mylogfile.txt" />
  <appendToFile value="true" />
  <lockingModel type="log4net.Appender.FileAppender+MinimalLock" />
  <layout type="log4net.Layout.PatternLayout">
    <conversionPattern value="%date [%thread] %level %logger - %message%newline" />
  </layout>
  <filter type="log4net.Filter.LevelRangeFilter">
    <levelMin value="INFO" />
    <levelMax value="FATAL" />
  </filter>
</appender>

Rolling File Appender

This is an appender that should be used in place of the file appender whenever possible. The purpose of the rolling file appender is to perform the same functions as the file appender but with the additional option to only store a certain amount of data before starting a new log file. This way, you won't need to worry about the logs on a system filling up over time. Even a small application could overwhelm a file system given enough time writing to a text file if the rolling option were not used. In this example, I am logging in a similar fashion to the file appender above, but I am specifying that the log file should be capped at 10MB and that I should keep up to 5 archive files before I start deleting them (oldest gets deleted first). The archives will be named with the same name as the file, only with a dot and the number after it (example:mylogfile.txt.2 would be the second log file archive). The staticLogFileName entry ensures that the current log file will always be named what I specified in the file tag (in my case, mylogfile.txt).

<appender name="RollingFileAppender" type="log4net.Appender.RollingFileAppender">
  <file value="mylogfile.txt" />
  <appendToFile value="true" />
  <rollingStyle value="Size" />
  <maxSizeRollBackups value="5" />
  <maximumFileSize value="10MB" />
  <staticLogFileName value="true" />
  <layout type="log4net.Layout.PatternLayout">
    <conversionPattern value="%date [%thread] %level %logger - %message%newline" />
  </layout>
</appender>

ADO.NET Appender

See http://www.codeproject.com/Articles/140911/log4net-Tutorial

The Code

Once you have a reference to the log4net DLL in your application, there are three lines of code that you need to know about. The first is a one-time entry that needs to be placed outside of your class. I usually put it right below my using statements in the Program.cs file. You can copy and paste this code since it will probably never need to change (unless you do something unusual with your config file). Here is the code:

[assembly: log4net.Config.XmlConfigurator(Watch = true)]

The next entry is done once per class. It creates a variable (in this case called "log") that will be used to call the log4net methods. This code is also code that you can copy and paste (unless you are using the Compact Framework). It does a System.Reflection call to get the current class information. This is useful because it allows us to use this code all over but have the specific information passed into it in each class. Here is the code:

private static readonly log4net.ILog log = log4net.LogManager.GetLogger
    (System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

The final code piece is the actual call to log some piece of information. This can be done using the following code:

log.Info("Info logging");

Notice that you can add an optional parameter at the end to include the exception that should be logged. Include the entire exception object if you want to use this option. The call is very similar, and it looks like this:

log.Error("This is my error", ex);

ex is the exception object. Remember that you need to use the %exception pattern variable in your appender to actually capture this exception information.

Config File Template

While you can look at the example code I have posted to see a config file in action, based upon some of the difficulties people were experiencing, I decided to post a config file template to help readers visualize where each of the config file pieces will go. I have given you a blank template below. I have also labeled each section with which level it is in so that, in case the formatting doesn't make it obvious, you know how each item relates to all the others up and down the tree.

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<!--This is the root of your config file-->
<configuration> <!-- Level 0 -->
  <!--This specifies what the section name is-->
  <configSections> <!-- Level 1 -->
    <section name="log4net" 
      type="log4net.Config.Log4NetConfigurationSectionHandler, 
            log4net"/> <!-- Level 2 -->
  </configSections>
  <log4net> <!-- Level 1 -->
    <appender>  <!-- Level 2 -->
      <layout>  <!-- Level 3 -->
        <conversionPattern />  <!-- Level 4 -->
      </layout>
      <filter>  <!-- Level 3 -->
      </filter>
    </appender>
    <root> <!-- Level 2 -->
      <level /> <!-- Level 3 -->
      <appender-ref /> <!-- Level 3 -->
    </root>
    <logger> <!-- Level 2 -->
      <level /> <!-- Level 3 -->
      <appender-ref /> <!-- Level 3 -->
    </logger>
  </log4net>
</configuration>

FAQs

1. Why can't I write to my text file? log4net runs under the privileges of the active user. Make sure that the active user has rights to create/modify/delete the specified text file.
2. Why aren't certain events being logged? Most likely, this is because you have a filter in place. Remember that the root entry can have an overall minimum log filter that specifies no event gets logged below this level. The actual appender can also have a level filter, or you could have the deny all in place too early.
3. Why am I logging events that I don't want? Most likely you have set a filter improperly. Either you forgot the deny all filter, or you included a level range filter first.
4. Why am I getting a compile error? If you get an error similar to "The referenced assembly "log4net" could not be resolved because it has a dependency on "System.Web, Version=4.0.0.0 ...", then you haven't changed your target framework to ".NET Framework 4". Change that and this error, along with others that cascade from it, will go away.  Note: this has been fixed in the new version of log4net.  You should no longer need to do this.
5. How do I use this in ASP.NET? Using this information in ASP.NET is the same as using it in a desktop application. The major difference is that the config file is the web.config file instead of the app.config file.
6. Why can't I get my ADO.NET appender to log anything? If you look over all of the settings and they look right, chances are that you are experiencing the pain of the bufferSize configuration. Change thebufferSize to 1 and it will attempt to log every message you send right away. If this still does not work, the issue is your configuration.

Source sample
Following is a simple ASP.Net sample
WebSiteTestLog4Net

Default.aspx.cs

[assembly: log4net.Config.XmlConfigurator(Watch = true)]




public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        log.Debug("Debug logging _Default");
        log.Info("Info logging _Default");
        log.Warn("Warn logging _Default");
        log.Error("Error logging _Default");
        log.Fatal("Fatal logging _Default");
        Class1.callMe();
    }




    private static readonly log4net.ILog log = log4net.LogManager.GetLogger
    (System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);
}

Class1.cs

/// 

/// Summary description for Class1
/// 
public class Class1
{
 public static void callMe()
    {
        log.Debug("Debug logging Class1");
        log.Info("Info logging Class1");
        log.Warn("Warn logging Class1");
        log.Error("Error logging Class1");
        log.Fatal("Fatal logging Class1");
    }
    private static readonly log4net.ILog log = log4net.LogManager.GetLogger
    (System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);
}

Web.config

Running the application will produce the following :

A file name mylogfile1 under the web site root :

Visual studio Output windows

Sources :

• http://www.codeproject.com/Articles/140911/log4net-Tutorial

Nathan