Get error message php

error_get_last

(PHP 5 >= 5.2.0, PHP 7, PHP

error_get_last — Get the last occurred error

Description

Gets information about the last error that occurred.

Parameters

This function has no parameters.

Return Values

Returns an associative array describing the last error with keys «type», «message», «file» and «line». If the error has been caused by a PHP internal function then the «message» begins with its name. Returns null if there hasn’t been an error yet.

Examples

Example #1 An error_get_last() example

The above example will output something similar to:

See Also

User Contributed Notes 13 notes

[Editor’s note: as of PHP 7.0.0 there is error_clear_last() to clear the most recent error.]

To clear error_get_last(), or put it in a well defined state, you should use the code below. It works even when a custom error handler has been set.

// var_dump or anything else, as this will never be called because of the 0
set_error_handler ( ‘var_dump’ , 0 );
@ $undef_var ;
restore_error_handler ();

// error_get_last() is now in a well known state:
// Undefined variable: undef_var

Function error_get_last() will return an error information even if the error is hidden because you’ve used character @, because of the «error_reporting» directive in the php.ini file, or because you’ve used function error_reporting().

( E_ALL ^ E_NOTICE );
$y = $x ;
$err = error_get_last ();
var_export ( $err );
?>
Will display: array ( ‘type’ => 8, ‘message’ => ‘Undefined variable: x’, ‘file’ => ‘test.php’, ‘line’ => 4, )

= @ $x ;
$err = error_get_last ();
var_export ( $err );
?>
Will display: array ( ‘type’ => 8, ‘message’ => ‘Undefined variable: x’, ‘file’ => ‘test.php’, ‘line’ => 4, )

The error_get_last() function will give you the most recent error even when that error is a Fatal error.

function handleFatalPhpError () <
$last_error = error_get_last ();
if( $last_error [ ‘type’ ] === E_ERROR ) <
echo «Can do custom output and/or logging for fatal error here. » ;
>
>

To know if something happened between two statements one can of course use a special string with user_error() (in lieu of a built-in special reset mentioned by mail at mbaierl dot com): @ user_error ( $error_get_last_mark = ‘error_get_last mark’ );
$not_set ;
$error_get_last = error_get_last ();
$something_happened =( $error_get_last [ ‘message’ ]!= $error_get_last_mark ); ?>

If your (function) ?> function returns true then you’ll have to roll you own error_get_last functionality. (Shortly mentioned by dmgx dot michael at gmail dot com).

To manual moderators: Re php.net/manual/add-note.php: Since i guess the above technically sorts under «References to other notes» i feel the need to defend myself with that i’m thinking it might show for usability where other’s say it fails and no, i haven’t got any other medium to reach the readers of the php manual notes.
Also, you could have some examples of what notes you think is okay. Thanks for your moderation.

Like $php_errormsg, the return value of this function may not be updated if a user-defined error handler returns non-FALSE. Tested on PHP 5.2.6.

( PHP_VERSION );
// Outputs: string(5) «5.2.6»

@ trigger_error ( «foo» );
$e = error_get_last ();
var_dump ( $e [ ‘message’ ]);
// Outputs: string(3) «foo»

set_error_handler ( create_function ( ‘$a,$b’ , » ));

@ trigger_error ( «bar» );
$e = error_get_last ();
var_dump ( $e [ ‘message’ ]);
// Outputs: string(3) «foo»

set_error_handler ( create_function ( ‘$a,$b’ , ‘return false;’ ));

@ trigger_error ( «baz» );
$e = error_get_last ();
var_dump ( $e [ ‘message’ ]);
// Outputs: string(3) «baz»
?>

Beware that registing a shutdown function to catch errors won’t work if other shutdown functions throw errors.

( ‘cleanupObjects’ );
register_shutdown_function ( ‘handleFatalPhpError’ );

function cleanupObjects () <
trigger_error ( ‘An insignificant problem’ , E_USER_WARNING );
>

function handleFatalPhpError () <
$last_error = error_get_last ();
if( $last_error [ ‘type’ ] === E_ERROR || $last_error [ ‘type’ ] === E_USER_ERROR ) <
echo «Can do custom output and/or logging for fatal error here. » ;
>
>

trigger_error ( ‘Something serious’ , E_USER_ERROR );

?>

In the above code, $last_error will contain the warning, becuase cleanupObjects() is called first.

This is a simple debugging script for mail functions.

//Built By Manomite for Debugging

error_reporting ( E_ALL ^ E_NOTICE );
$err = error_get_last ();

$res = «An error has occurred in your application sir.n Details Include » . $err . «»

mail ( «admin@manomite.net» , «Error Occurred» , $res , $from );
>
>
>
?>

If you have the need to check whether an error was a fatal error before PHP 5.2 (in my case, within an output buffer handler), you can use the following hack:

# Check if there was a PHP fatal error.
# Using error_get_last is the «right» way, but it requires PHP 5.2+. The back-up is a hack.
if ( function_exists ( ‘error_get_last’ )) <
$lastPHPError = error_get_last ();
$phpFatalError = isset( $lastPHPError ) && $lastPHPError [ ‘type’ ] === E_ERROR ;
> else <
$phpFatalError = strstr ( $output , ‘Fatal error:’ ) && ! strstr ( $output , ‘ ‘ );
>
?>

This is, of course, language-dependent, so it wouldn’t be good in widely-distributed code, but it may help in certain cases (or at least be the base of something that would work).

While mail at mbaierl dot com makes the point that this function isn’t best for reporting the possible error condition of the most recently executed step, there are situations in which it is especially helpful to know the last error—regardless of when it occurred.

As an example, imagine if you had some code that captured the output from dynamic pages, and cached it for faster delivery to subsequent visitors. A final sanity check would be to see if an error has occurred anywhere during the execution of the script. If there has been an error, we probably don’t want to cache that page.

Источник

error_log

(PHP 4, PHP 5, PHP 7, PHP

error_log — Send an error message to the defined error handling routines

Description

Sends an error message to the web server’s error log or to a file.

Parameters

The error message that should be logged.

Says where the error should go. The possible message types are as follows:

error_log() log types

The destination. Its meaning depends on the message_type parameter as described above.

The extra headers. It’s used when the message_type parameter is set to 1 . This message type uses the same internal function as mail() does.

Return Values

Returns true on success or false on failure. If message_type is zero, this function always returns true , regardless of whether the error could be logged or not.

Changelog

Examples

Example #1 error_log() examples

// Send notification through the server log if we can not
// connect to the database.
if (! Ora_Logon ( $username , $password )) <
error_log ( «Oracle database not available!» , 0 );
>

// Notify administrator by email if we run out of FOO
if (!( $foo = allocate_new_foo ())) <
error_log ( «Big trouble, we’re all out of FOOs!» , 1 ,
«operator@example.com» );
>

// another way to call error_log():
error_log ( «You messed up!» , 3 , «/var/tmp/my-errors.log» );
?>

Notes

error_log() is not binary safe. message will be truncated by null character.

message should not contain null character. Note that message may be sent to file, mail, syslog, etc. Use appropriate conversion/escape function, base64_encode() , rawurlencode() or addslashes() before calling error_log() .

User Contributed Notes 20 notes

Advice to novices: This function works great along with «tail» which is a unix command to watch a log file live. There are versions of Tail for Windows too, like Tail for Win32 or Kiwi Log Viewer.

Using both error_log() and tail to view the php_error.log you can debug code without having to worry so much about printing debug messages to the screen and who they might be seen by.

Further Note: This works even better when you have two monitors setup. One for your browser and IDE and the other for viewing the log files update live as you go.

DO NOT try to output TOO LARGE texts in the error_log();

if you try to output massive amounts of texts it will either cut of the text at about 8ooo characters (for reasonable massive strings,

There is a limit on the maximum length that you can pass as the $message.

The default seem to be 1024 but can be changed by adjusting the value of the runtime configuration value of ‘log_errors_max_len’.

Beware! If multiple scripts share the same log file, but run as different users, whichever script logs an error first owns the file, and calls to error_log() run as a different user will fail *silently*!

Nothing more frustrating than trying to figure out why all your error_log calls aren’t actually writing, than to find it was due to a *silent* permission denied error!

when using error_log to send email, not all elements of an extra_headers string are handled the same way. «From: » and «Reply-To: » header values will replace the default header values. «Subject: » header values won’t: they are *added* to the mail header but don’t replace the default, leading to mail messages with two Subject fields.

( «sometext» , 1 , «zigzag@my.domain» ,
«Subject: FoonFrom: Rizzlas@my.domainn» );

You can easily filter messages sent to error_log() using «tail» and «grep» on *nix systems. This makes monitoring debug messages easy to see during development.

Be sure to «tag» your error message with a unique string so you can filter it using «grep»:

error_log(«DevSys1 — FirstName: $FirstName — LastName: $Lastname»);

On your command line:

tail -f /var/log/httpd/error_log | grep DevSys1

In this example, we pipe apache log output to grep (STDIN) which filters it for you only showing messages that contain «DevSys1».

The «-f» option means «follow» which streams all new log entries to your terminal or to any piped command that follows, in this case «grep».

Relative paths are accepted as the destination of message_type 3, but beware that the root directory is determined by the context of the call to error_log(), which can change, so that one instance of error_log () in your code can lead to the creation of multiple log files in different locations.

In a WordPress context, the root directory will be the site’s root in many cases, but it will be /wp-admin/ for AJAX calls, and a plugin’s directory in other cases. If you want all your output to go to one file, use an absolute path.

When logging to apache on windows, both error_log and also trigger_error result in an apache status of error on the front of the message. This is bad if all you want to do is log information. However you can simply log to stderr however you will have to do all message assembly:

LogToApache($Message) <
$stderr = fopen(‘php://stderr’, ‘w’);
fwrite($stderr,$Message);
fclose($stderr);
>

«It appears that the system log = stderr if you are running PHP from the command line»

Actually, it seems that PHP logs to stderr if it can’t write to the log file. Command line PHP falls back to stderr because the log file is (usually) only writable by the webserver.

Note that since typical email is unencrypted, sending data about your errors over email using this function could be considered a security risk. How much of a risk it is depends on how much and what type of information you are sending, but the mere act of sending an email when something happens (even if it cannot be read) could itself imply to a sophisticated hacker observing your site over time that they have managed to cause an error.

Of course, security through obscurity is the weakest kind of security, as most open source supporters will agree. This is just something that you should keep in mind.

And of course, whatever you do, make sure that such emails don’t contain sensitive user data.

Another trick to post «HTML» mail body. Just add «Content-Type: text/html; charset=ISO-8859-1» into extra_header string. Of course you can set charset according to your country or Env or content.

stuff

«,1,»eat@joe.com»,»subject :lunchnContent-Type: text/html; charset=ISO-8859-1″);

//Multiline error log class
// ersin güvenç 2008 eguvenc@gmail.com
//For break use «n» instead ‘n’

Class log <
//
const USER_ERROR_DIR = ‘/home/site/error_log/Site_User_errors.log’ ;
const GENERAL_ERROR_DIR = ‘/home/site/error_log/Site_General_errors.log’ ;

/*
User Errors.
*/
public function user ( $msg , $username )
<
$date = date ( ‘d.m.Y h:i:s’ );
$log = $msg . » | Date: » . $date . » | User: » . $username . «n» ;
error_log ( $log , 3 , self :: USER_ERROR_DIR );
>
/*
General Errors.
*/
public function general ( $msg )
<
$date = date ( ‘d.m.Y h:i:s’ );
$log = $msg . » | Date: » . $date . «n» ;
error_log ( $msg . » | Tarih: » . $date , 3 , self :: GENERAL_ERROR_DIR );
>

$log = new log ();
$log -> user ( $msg , $username ); //use for user errors
//$log->general($msg); //use for general errors
?>

Depending on the error, you may also want to add an error 500 header, and a message for the user:

$message = ‘Description of the error.’;
error_log($message);
header($_SERVER[‘SERVER_PROTOCOL’] . ‘ 500 Internal Server Error’, true, 500);
exit($message);

When error_log() unexpectedly uses stdout, you should check if the php.ini value for error_log is empty in your CLI environment. Something as simple as this might restore expected behavior:

After scouring the internet for getting event logging to
work in syslog on Windows 2003, I found the following
from this post and was able to successfully get Windows
Event Viewer to log PHP errors/notices:

Источник

The Essential Guide to PHP Error Logging

PHP has been one of the top (if not best) server-side scripting languages in the world for decades. However, let’s be honest – error logging in PHP is not the most straightforward or intuitive. It involves tweaking a few configuration options plus some playing around to get used to. Once you have everything set up and figured out (like you will after reading this post), things seem much easier, and you realize how helpful error logging can turn out to be for your application – from debugging and troubleshooting to monitoring and maintenance. 

And this is why we are covering error logging in PHP in this post. We will start by revisiting the importance of logging errors in your application. We will then explore errors in PHP – their different types, and how they can be output. Next, we will look at all the error logging configurations in PHP, and understand how we can tweak these to our liking, before we see some error logging examples, and explore functions in PHP that allow us to write errors to log files. This post is a complete guide to error logging in PHP.

Here’s an outline of what we’ll be covering so you can easily navigate or skip ahead in the guide: 

• Importance of Logging Errors 
• PHP Error Types
• Where Can PHP Errors be Output
• Enabling and Configuring Error Reporting in PHP 
• Logging Errors in PHP 
• PHP’s Error Logging Functions 
• error_log()
• trigger_error()
• syslog()
• set_error_handler()
• Popular PHP Logging Libraries 

Importance of Logging Errors 

Errors in software systems have this terrible reputation of being associated with failing things and breaking functionality. As a result, many of us often fail to recognize the importance of these loud red strings that bring our attention to faults, inconsistencies, and inaccuracies in our code – mistakes that can cost us dearly if allowed to fall through the cracks. Therefore, it is worthwhile for some of us to change our outlook towards error messages – to track, log, and organize them – and embrace their importance. 

There’s a reason developers and organizations build and leverage dedicated logging systems that keep track of errors that arise throughout an application’s lifecycle. These logs provide useful information about what went wrong, when, where, and how it can be fixed. 

For small-scale personal projects, it is common for developers not to feel the need to spend time setting up an effective logging system. This seems plausible because your code and end-user interactions are much more manageable for smaller projects. However, the requirement for effectively logging and maintaining errors and other information grows exponentially as your application scales. For larger applications, catering to thousands of users, it becomes unwieldy to track errors and updates across hundreds of components in real-time. Putting in place a system that can record the status of the very many events that an application’s operation entails allows organizations to maintain a clear record of their performance. This allows for more transparency and therefore ensures that no issues go unnoticed. As a result, this makes your application more reliable, easy to maintain, monitor, and debug.

Now that we are hopefully convinced that error logging is a worthwhile expedition, let us look at the different types of errors in PHP.

PHP Error Types

Broadly, there are five types of errors in PHP:

1. Fatal run-time Errors (E_ERROR) 

These errors typically happen when an operation in your code cannot be performed. This leads to your code exiting. An example of a fatal error would be when you call a function that hasn’t been defined in your code, shown below:

<?php
function foo() {
  echo "Function foo called.";
}
boo(); // undefined function 'boo'
?>

Error output –>

Fatal error: Uncaught Error: Call to undefined function boo() in code/my-php/index.php:5 Stack trace: #0 {main} thrown in code/my-php/index.php on line 5.

2. Warning Errors (E_WARNING)

A warning error is more gentle and less obtrusive in that it does not halt the execution. It presents a friendly reminder of something amiss in your code – a mistake that might not fail things immediately or fail anything at all but suggests a more accurate way of doing things that make your code more foolproof. These warnings can also save developers from issues that might pose a much bigger threat in the future. An example of a warning error would be when you try to include a file in PHP using an incorrect file path, as shown below:

<?php
include('filename.txt'); // arbitrary file that is not present
echo "Hello world";
?>

Error output ->

Warning: include(filename.txt): failed to open stream: No such file or directory in code/my-php/index.php on line 2

3. Parse Errors (E_PARSE)

Parse errors are also known as syntax errors as they arise from syntactical mistakes in your code. These errors are raised during the compilation of your code, making it exit before it runs. A common example of a parse error is missing a semicolon at the end of a code statement, shown below:

<?php
echo Hello world // no quotes or semicolon used
?>

Error output ->

Parse error: syntax error, unexpected 'world' (T_STRING), expecting ',' or ';' in code/my-php/index.php on line 2.

4. Notice Errors (E_NOTICE)

Notice errors are minor errors that are encountered during run-time, and just like warning errors, do not halt the execution. They usually occur when the script is attempting to access an undefined variable, for example, as shown below:

<?php
$a = 1;
$c = $a + $b; // undefined variable $b
?>

Error output ->

Notice: Undefined variable: b in code/my-php/index.php on line 3

5. User Errors (E_USER_ERROR, E_USER_WARNING, E_USER_NOTICE) 

User errors are user-defined, i.e., present a custom user-generated message raised explicitly from the code to capture a specific condition. These errors are manually raised by developers using the trigger_error function instead of the PHP engine. They are further classified as fatal, warning, and notice errors, but we’ll group them all as user errors for simplicity.

Where can PHP Errors be Output?

There are two primary places where we can have our errors presented in PHP – through inline errors and dedicated error log files.

Inline Errors 

Inline errors are those that show up on your webpage in the browser or your terminal via STDOUT in a command-line environment. These errors prove to be quite useful during development – for developers to debug their code, fix issues, and get information about the overall execution. Below is an example of what these errors usually look like in the browser:

Though this proves to be super helpful for developers, you should be very careful in ensuring that these errors are not output when your application goes into production – for two reasons – end-user experience and security. You can toggle the displaying of these errors using the display_error directive in your system’s configuration. We’ll dive deeper into this in the next section.

Error Log Files 

Inline errors are not persistent in memory, i.e., they are not saved anywhere and are only viewed as long as the browser or terminal session is alive. Additionally, you’ll only want to have them in a development environment. Conversely, as the theme of this post suggests, logging your errors is the more intelligent and more systematic approach towards maintaining large-scale applications. These are persistent in memory and provide information about the operation of your application across multiple components in one place, making it easier for monitoring and troubleshooting.

PHP, therefore, allows you to direct all your errors to specific log files; these files store timestamps, error stack traces, custom messages, and other helpful information about the source of the error and how to fix it. You can specify the path of your custom log file using the error_log directive of your system configuration. Here’s an example of an error log file:

You can also choose to have your errors logged to the system’s log file, usually located in – /var/log/syslog. We’ll cover this in a later section in the post.

Now let’s look at how we can configure where and how we want our errors logged.

Enabling and Configuring Error Reporting in PHP 

As we discussed previously, logging in PHP is slightly less straightforward than other languages and frameworks. You might have to tweak a few options in configuration files to customize logging patterns. For example, when you install PHP on your machine, the initial configuration comes with some aspects of error logging disabled. This differs from system to system, and therefore, you should manually check these settings before getting started.

Logging Configuration Options in php.ini File

The configuration options are in the php.ini file. This file is read when PHP starts up and allows developers to play around with PHP’s functionality. Usually, this file can be found somewhere in the /etc/php directory on most Linux systems. 

There are a bunch of directives (options) pertaining to the logging of errors in PHP that we can configure in this php.ini file:

• display_errors (default: 1)

Display errors are the inline errors we previously looked at. This directive can be used to good effect during development to output PHP error messages to the browser or terminal. However, for applications in production, you should likely turn this off to save your users from a poor website experience due to obscure error messages. Not only that, but this also protects you from exposing valuable information about the internals of your application as a security measure.

• display_startup_errors (default: 0)

As the name suggests, this is to output any errors that take place when PHP starts up. These usually do not provide any valuable information about your application specifically, and therefore need not be turned on.

• log_errors (default: 0)

This directive allows you to toggle the logging of errors to the specified path (in the next directive). Because this is turned off by default, it would be advisable to toggle this to 1 for recording your application’s error messages in a log file.

• error_log (default: 0)

This directive allows you to specify the path of your log file. You can also set this to “syslog” for directing all your error log messages to the system log. 

• error_reporting (default: null)

The error_reporting directive allows you to customize which error levels you want reported, and which you are okay with going unreported. For example, you can use the directive as shown below to have all errors reported: error_reporting = E_ALL

• track_errors (default: 0)

This directive allows you to access the last raised error message in the $php_errormsg global variable in your code and can keep track of errors across your whole project.

After making changes to your php.ini file, you will need to restart the server for the changes to take effect.

The ini_set() Function

However, if you are unable to locate the php.ini file, or prefer overriding your project’s global configuration options, there is also an option to update these directives using the ini_set() function in your PHP code. For example, the below code can be used for customizing error reporting in your project:

<?php

// enabling error logging
ini_set('log_errors', 1);  

// Customize reporting of errors
ini_set('error_reporting', E_WARNING | E_ERROR | E_PARSE | E_NOTICE);

// specify error log file path
ini_set('error_log', '/tmp/my-logs.log');

?>

The error_reporting() Function

One can also modify the error_reporting configuration option using the error_reporting() function from inside your code during run-time. As in the ini_set function, you can use bitwise operators like OR (|), AND (&), NOT (~), etc., when specifying the error levels to be reported. Below are a few examples of how this function can be used.

// Report only selected kinds of errors
error_reporting(E_ERROR | E_PARSE | E_NOTICE);

or

// Report all errors except E_WARNING
error_reporting(E_ALL & ~E_WARNING);

Now that we have got the system configurations and overall setup out of the way, let’s look at an example of how errors in your project code can be logged to files on your system.

Logging Errors in PHP

First, we will override the logging configuration parameters using the ini_set() function to enable error logging and specify the log file’s path. Then we’ll write some erroneous code to have PHP raise an error that we would like to have logged.

<?php
  ini_set('log_errors', 1); // enabling error logging
  ini_set('error_log', '/path/my-error-file.log'); // specifying log file path

  echo $b; // undefined variable should raise error
?>

After opening the web page on our browser, let’s open the ‘my-error-file.log’ file to see if the error message was logged. Here is the log file output:

[28-Feb-2021 13:34:36 UTC] PHP Notice:  Undefined variable: b in code/my-php/index.php on line 5

As you can see, our notice error was logged with a timestamp. As our code encounters more and more errors, this file will keep getting populated with corresponding timestamps. Note that we haven’t explicitly turned off display_errors, so these error messages are likely to be logged to the browser web page – something you might want to avoid during production. 

This was an example of capturing errors raised by PHP in log files. Now let’s look at how we can raise and log custom error messages for our application.

PHP’s Error Logging Functions

So far, we looked at errors raised by PHP – errors about your code execution. However, oftentimes you would want to also capture custom errors, with custom error messages specific to the functioning of your application. These so-called errors might not necessarily fail your code or halt its execution, but can indicate conditions characterized as erroneous and noteworthy for your application. These can act as indications to the organization about anomalous behavior that the team might want to look into and fix.

To facilitate this, PHP provides a set of functions that we can use to actively log errors in our code.

error_log()

The most common method for actively logging errors is the error_log() function. This sends a string argument for the error message to the log file.

error_log (string $message, int $message_type=0, string $destination=?, string $extra_headers=?) : bool

It also takes many other parameters to send error messages over email or specific log files. However, for the sake of simplicity, we won’t be covering that here. 

The interesting thing about this function is it logs your error message to the file specified in the configuration (or to the system log), regardless of the value of the log_errors directive. Let’s take a very simple example of logging an error when a specific condition in our code is met.

<?php

ini_set('error_log', '/path/my-error-file.log');
$a = 5;
$b = 10;

$c = $a + $b;

if ($c < 20) {
error_log("Sum is less than 20."); // logging custom error message
}

?>

Here is the output of the log file:

[28-Feb-2021 13:31:50 UTC] Sum is less than 20

Similarly, you can also log the values of variables in your code to provide additional context about your errors. Let’s see an example for that:

<?php
  ini_set('error_log', '/path/my-error-file.log');

  $languagesArray = array("PHP", "Python", "Node.js");
  error_log("Lorem ipsum. Array data -> ".print_r($languagesArray, true));
?>

Here’s the output of the log file ->

[28-Feb-2021 13:49:28 UTC] Lorem ipsum. Array data -> Array
(
   [0] => PHP
   [1] => Python
   [2] => Node.js
)

trigger_error()

The trigger_error() function can be used to raise a user-defined error/warning/notice. You can also specify the error type based on the condition. This allows you to customize its reporting and other behavior – for example, using an error type of E_USER_ERROR. We can cause the code to exit immediately compared to an E_USER_WARNING error.

trigger_error (string $error_msg, int $error_type=E_USER_NOTICE) : bool

The difference between trigger_error and error_log is that the former only generates a user error and depends on your system’s logging configurations to handle this error message (whether displayed or logged). error_log, on the other hand, will log your message regardless of the system’s configuration.

Here is the code for the same example we saw previously:

<?php
ini_set('log_errors', 1); // enabling error logging
ini_set('error_log', '/path/my-error-file.log'); // specifying log file path

$a = 5;
$b = 10;
$c = $a + $b;

if ($c < 20) {
trigger_error("Sum is less than 20.", E_USER_ERROR);
      echo "This will not be printed!";
}

?>

This adds a similar log entry to what we saw previously, but with an error level, plus the conventional error source information (log file output below):

[01-Mar-2021 01:16:56 UTC] PHP Fatal error:  Sum is less than 20. in code/my-php/index.php on line 10

syslog()

You can also choose to directly send an error message to the system’s log using the syslog() function.

syslog (int $priority, string $message) : bool

The first argument is the error’s priority level – LOG_ERR, LOG_WARNING, LOG_NOTICE, LOG_ALERT, LOG_EMERG, etc. (more about it here).  The second argument is the actual message’s text. This is how the function can be used:

<?php
// opening logger connection
openlog('myApp', LOG_CONS | LOG_NDELAY | LOG_PID, LOG_USER | LOG_PERROR
); // more information about params in documentation

syslog(LOG_WARNING, "My error message!");

closelog();
?>

This should reflect in your system’s logger (usually in /var/log/syslog) as:

Mar 1 13:27:15 zsh php: My error message! 

set_error_handler()

To customize the handling of all the user-defined errors throughout your code, PHP allows you to specify a custom error handler function to override the default handling of errors. This makes it easy for organizations to modify how they want their errors logged, the corresponding error messages send method, and much more. The set_error_handler() function helps with this.

set_error_handler (callable $error_handler, int $error_types=E_ALL | E_STRICT) : mixed

It takes as an argument our custom error handler function, which will define the handling of our errors, and look something like this:

handler (int $errno, string $errstr, string $errfile=?, int $errline=?, array $errcontext=?) : bool

This takes in many parameters like the error number, error string, corresponding file, etc. Let’s understand this better using the same previous example:

<?php
// custom error handler function ->
function myErrorHandler($errno, $errstr, $errfile, $errline, $errcontext){
    $message = date("Y-m-d H:i:s - "); // timestamp in error message
    $message .= "My Error: [" . $errno ."], " . "$errstr in $errfile on line $errline, n"; // custom error message
    $message .= "Variables:" . print_r($errcontext, true) . "rn";
   
    error_log($message, 3, "/path/my-error-file.log");
    die("There was a problem, please try again."); // exit code
}

set_error_handler("myErrorHandler");

$a = 5;
$b = 10;
$c = $a + $b;

if ($c < 20) {
trigger_error("Sum is less than 20.", E_USER_WARNING);
}

echo "This will not be printed!";
?>

Here, we define a custom error handler function where we modify the error message a bit, log it, and exit the code. Then, when we use the trigger_error() function, its logging is handled by the above function, which takes care of the rest. This is what the output in the log file looks like:

2021-03-01 06:58:07 - My Error: [512], Sum is less than 20. in code/my-php/index.php on line 22,
Variables:Array
(
   [a] => 5
   [b] => 10
   [c] => 15
)

As you can see, this can be used to fully customize error logging in applications, allowing organizations to prioritize aspects of errors and contexts that are more important for their application.

Popular PHP Logging Libraries 

Thanks to the huge PHP community support on the internet, there have been very many logging libraries that aim to provide more functionality and ease the overall process for developers and organizations. Each of the renowned PHP frameworks that you must have heard of come equipped with logging libraries built-in. There are also now logging standards established, like the PSR-3 (PHP Standards Recommendation) logger interface, that defines a standardized interface to follow for logging libraries. 

Below is a list of some of the most popular logging libraries in PHP:

• Monolog
• Analog
• KLogger
• Log4PHP

Feel free to check these out to see what default error logging in PHP is missing out on.

Wrapping Up 

In this post, we covered everything about errors and logging in PHP. We discussed the importance of logging mechanisms in your application, looked at the different types of errors in PHP, and explored the various configuration options and PHP functions that we can use to log errors effectively.

Now that you have a decent understanding of everything, go ahead and start implementing error logging for your application! It doesn’t matter if you are working on a small project where things might seem under control even without log files. Logging your errors is considered one of the top “best practices” in software development that becomes exponentially more important as your applications grow and scale.

To learn more about logging in PHP in general, feel free to check out the Tutorial: Log to Console in PHP on our blog!

To up your application monitoring game by identifying bottlenecks and gaining effective application performance insights, check out ScoutAPM to get started with a 14-day free trial!

Happy coding!