(PHP 4, PHP 5, PHP 7)

syslogGenera un mensaje log de sistema


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

syslog() genera un mensaje log que será distribuido por el logger del sistema.

Para información de como configurar un usuario definido como controlador del log, ver syslog.conf (5) del manual de Unix. Más información sobre los recursos y opciones de syslog pueden encontrarse en las páginas del manual de syslog (3) en entornos Unix.



priority es una combinación del tipo y el nivel. Posibles valores:

Prioridades syslog() (en orden descendente)
Constante Descripción
LOG_EMERG sistema inservible
LOG_ALERT se debe tomar acción de forma inmediata
LOG_CRIT condiciones críticas
LOG_ERR condiciones de error
LOG_WARNING condiciones de alerta
LOG_NOTICE condición normal, pero relevante
LOG_INFO mensaje de información
LOG_DEBUG mensaje de testeo


El mensaje a enviar a excepción de dos caracteres %m serán reemplazados con el mensaje de error (strerror) correspondiente con el valor presente de errno.

Valores devueltos

Devuelve TRUE en caso de éxito o FALSE en caso de error.


Ejemplo #1 Uso de syslog()

// abre syslog, incluyendo el ID del proceso. También envia al
// log el error estándar y el mecanismo de logging
// definido por el usuario
openlog("myScriptLog"LOG_PID LOG_PERRORLOG_LOCAL0);

// algún código

if (authorized_client()) {
// hace algo
} else {
// Cliente no autorizado!
    // Se logea el intento
$access date("Y/m/d H:i:s");
syslog(LOG_WARNING"Cliente no autorizado: $access {$_SERVER['REMOTE_ADDR']} ({$_SERVER['HTTP_USER_AGENT']})");



En Windows NT, el servicio syslog es emulado usando el Event Log.


El uso de LOG_LOCAL0 a través de LOG_LOCAL7 para el parámetro facility de openlog() no está disponible en Windows.

Ver también

  • openlog() - Open connection to system logger
  • closelog() - Cerrar conexión al log del sistema

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User Contributed Notes 16 notes

Antonio Lobato
8 years ago
A word of warning; if you use openlog() to ready syslog() and your Apache threads accept multiple requests, you *must* call closelog() if Apache's error log is configured to write to syslog.  Failure to do so will cause Apache's error log to write to whatever facility/ident was used in openlog.

Example, in httpd.conf you have:

ErrorLog syslog:local7

and in php you do:

("myprogram", 0, LOG_LOCAL0);
syslog("My syslog message");

From here on out, this Apache thread will write ErrorLog to local0 and under the process name "myprogram" and not httpd!  Calling closelog() will fix this.
helly at php dot net
11 years ago
If you are using syslog-ng and want errors send to syslog then use ini setting "error_log = syslog" and add something like the following to your syslog-ng.conf:

destination php { file("/var/log/php.log" owner(root) group(devel) perm(0620)); };
log { source(src); filter(f_php); destination(php); };
huangyg11 at gmail dot com
3 years ago
For those who want to simultaneously write to multiple syslog facilities :

syslog(LOG_INFO|LOG_LOCAL0, "message for local0");
syslog(LOG_INFO|LOG_LOCAL1, "message for local1");
james dot ellis at gmail dot com
11 years ago
If anyone is wondering why their log messages are appearing in multiple log files, here is one answer applying to *nix systems:

If your syslog.conf looks like this (assuming you use LOG_LOCAL0 for web app logging) :    /var/log/web/info.log

This will collect *all* messages of LOG_INFO level and higher, i.e everything except debug messages

Try this instead to ensure that only messages of the named log level go into the relevant log file:

local0.=info    /var/log/web/info.log

Additionally, you may like to add this to ensure your messages don't end up in generic log files like "messages"  "all" "syslog" and "debug":

local0.none    /var/log/messages
local0.none    /var/log/debug

saves disk space among other things - more at "man syslog.conf"
antoine dot leverve dot EXT at zodiacaerospace dot com
3 years ago
The documentation is incorrect when it says "Priorities (in descending order)", as the table that follows is actually in **ascending** order.

For example my output says:

An important difference, that caused me some pain!
stevekamerman at gmail dot com
2 months ago
This function sends messages in BSD Syslog RFC 3164 format (

To see the raw messages being sent by PHP to the logging socket, first stop your syslog/rsylsog/ng-syslog service, then listen to the logging socket with the netcat-openbsd package:

nc -U -l /dev/log

Now, log something from PHP:

(LOG_LOCAL1|LOG_INFO, "Test from PHP");

You will see the rfc3164 output from netcat:

<142>Oct 24 14:32:51 php: Test from PHP
daniele dot patoner at biblio dot unitn dot it
15 years ago
This work for me, to redirect  logs to a separate syslog file

put this line in your /etc/syslog.conf :

local0.debug   /var/log/php.log

Then restart syslogd:

/etc/init.d/syslog restart

php example:

openlog("TextLog", LOG_PID, LOG_LOCAL0);

$data = date("Y/m/d H:i:s");
syslog(LOG_DEBUG,"Messagge: $data");

gregj at pdxperts dot com
15 years ago
The message string sent to the log file is limited to 500 characters.
dpreece at paradise dot net dot nz
16 years ago
To set up a custom log file via the syslog daemon (FreeBSD in this case)...

Add to /etc/syslog.conf a line that says all errors from the httpd process are to go to a file called (for example) /var/log/httpd-php.log

*.*   {tab}   /var/log/httpd-php.log

Note the tab, being a tab character! Next create a blank file to be written to. I'm sure there are 1e+6 ways to do this, but I choose

# cat > httpd-php.log << EOF

Finally find your syslog daemon and send it a sighup to inform it of the change:

# ps ax | grep syslogd
  133  ??  Ss     0:07.23 syslogd -s
# kill -1 133

Et voila! Php syslog calls will now arrive in /var/log/httpd-php.log
nospam \100 jraxis com (that's right!)
16 years ago
This *does* actually goto the system log as configured in /etc/syslog.conf (such as /var/log/messages), it doesn't goto Apache's ErrorLog (such as /var/log/httpd/error_log). At least under my Debian Potato with Apache 1.3.23.

Use error_log() to be sure it gets into Apache's ErrorLog.
mavetju at chello dot nl
18 years ago
With FreeBSD I can use: syslog(LOG_INFO,"test");

BSD/OS does not support this, I had to use the literal values for the priority (158:
rcgraves+php at brandeis dot edu
18 years ago
For the-header-file-enabled:

man 3 syslog defines the priorities, but not the integer values. For that you'll need to read your system header file.

Let's suppose I want to log an informational message in the mail log (which happens to be true). The man page tells me I want LOG_MAIL|LOG_INFO. So I look in /usr/include/sys/syslog.h and find (this happens to be Linux, your system could be different):

#define LOG_INFO        6       /* informational */
#define LOG_MAIL        (2<<3)  /* mail system */

2<<3 means shift 3 bits left, which means multiply by 8. So I want 2*8 + 6 = 22. syslog(22,"this message will appear in the mail log"); And indeed it does.
bb at lb-data dot co dot at
19 years ago
In Windows NT, use the following values of priority:
1 = error,
6 = info
14 years ago
I had a problem trying to issue a syslog message with IIS 5.1 under Windows XP. The function call seemed to succeed, but the event viewer showed that no entry was made.
Finally I found out that the user account used for the webserver (IUSR_<Computername>) did not have enough permissions to issue syslog alerts. I changed this by adding this user to the Users group instead of only Guest.
adam _at_ lockdownnetworks _dot_ com
11 years ago
Be aware when using syslog() that if you set the timezone of environment to be something other than the standard, syslog() may log the time to the log(s) with the wrong time zone information. For example:



syslog(LOG_INFO, 'UTC Log line');

syslog(LOG_INFO, 'US/Pacific Log line');



Viewing the /usr/log/messages log will display these two lines:

Apr 11 01:25:39 hostname mylog[1400]: UTC Log line
Apr 10 18:25:39 hostname mylog[1400]: US/Pacific Log line

gherson at snet dot net
18 years ago
Example of where to look for syslog's output:   /var/log/httpd/access_log
(on Red Hat Linux Secure Server v6.2).
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