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PHP : Function Reference : Error Handling and Logging Functions : error_log


Send an error message somewhere (PHP 4, PHP 5)
bool error_log ( string message [, int message_type [, string destination [, string extra_headers]]] )

Example 593. 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,

// other ways of calling error_log():
error_log("You messed up!", 2, "");
error_log("You messed up!", 2, "loghost");
error_log("You messed up!", 3, "/var/tmp/my-errors.log");

Code Examples / Notes » error_log

28-mar-2003 10:14

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.
error_log("sometext", 1, "zigzag@my.domain",
 "Subject: Foo\nFrom: Rizzlas@my.domain\n");
To: zigzag@my.domain
Envelope-to: zigzag@my.domain
Date: Fri, 28 Mar 2003 13:29:02 -0500
From: Rizzlas@my.domain
Subject: PHP error_log message
Subject: Foo
Delivery-date: Fri, 28 Mar 2003 13:29:03 -0500
quoth the docs: "This message type uses the same internal function as mail() does."  
mail() will also fail to set a Subject field based on extra_header data - instead it takes a seperate argument to specify a "Subject: " string.
php v.4.2.3, SunOS 5.8


When outputting to syslog, it uses the syslog() function, which limits its output to 500 characters. We have been able to send multi-line output to the log, but newlines appear to be replaced with a space in the output, and output is cut off at 500 characters.
A simple workaround for long, multi-line output is something like this:
$errlines = explode("\n",$errmsg);
foreach ($errlines as $txt) { error_log($txt); }


On a Mac running OS X, for the error logging to work I needed to put this in my php.ini:
error_log = /tmp/php_errors.log
Attempting to put the log in other locations did not work, probably due to permission issues.


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.


It appears that the system log = stderr if you are running PHP from the command line, and that often stderr = stdout.  This means that if you are using a custom error to both display the error and log it to syslog, then a command-line user will see the same error reported twice.


It appears that error_log() only logs the first line of multi-line log messages. To log a multi-line message, either log each line individually or write the message to another file.


In the case of missing your entries in the error_log file:
When you use error_log in a script that does not produce any output, which means that you cannot see anything during the execution of the script, and when you wonder why there are no error_log entries produced in your error_log file, the reasons can be:
- you did not configure error_log output in php.ini
- the script has a syntax error and did therefore not execute


I find it very suprising that there are no PHP constants (or references to them if they exist) for the log types.  I would expect
or something to that nature.  Are we going to see this in any future versions?  Seems very silly to use integers here when they could easily be changed or confused.

p dot lhonorey

Hi !
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.
EG: Error_log("<html><h2>stuff</h2></html>",1,"","subject  :lunch\nContent-Type: text/html; charset=ISO-8859-1");
Enjoy !


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!


Beware the size of your custom error_log!
Once it exceeds 2GB the function errors, ending your script at the error_log() line.  I'm sure this differs from OS to OS, but I have seen it die writing to ext2 under modern Linux systems.

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