syslog

    (PHP 4, PHP 5, PHP 7, PHP 8)

    syslog — Generate a system log message

    Description

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

    syslog() generates a log message that will be distributed by the system logger.

    For information on setting up a user defined log handler, see the syslog.conf (5) Unix manual page. More information on the syslog facilities and option can be found in the man pages for syslog (3) on Unix machines.

    Parameters

    priority

    One of the LOG_EMERG, LOG_ALERT, LOG_CRIT, LOG_ERR, LOG_WARNING, LOG_NOTICE, LOG_INFO, LOG_DEBUG constants.

    message

    The message to send.

    Return Values

    Always returns true.

    Examples

    Example #1 Using syslog()

    <?php
    // open syslog, include the process ID and also send
    // the log to standard error, and use a user defined
    // logging mechanism
    openlog("myScriptLog", LOG_PID | LOG_PERROR, LOG_LOCAL0);

    // some code

    if (authorized_client()) {
    // do something
    } else {
    // unauthorized client!
    // log the attempt
    $access = date("Y/m/d H:i:s");
    syslog(LOG_WARNING, "Unauthorized client: $access {$_SERVER['REMOTE_ADDR']} ({$_SERVER['HTTP_USER_AGENT']})");
    }

    closelog();
    ?>

    Notes

    On Windows, the syslog service is emulated using the Event Log.

    Note:

    Use of LOG_LOCAL0 through LOG_LOCAL7 for the facility parameter of openlog() is not available in Windows.

    See Also

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    User Contributed Notes 8 notes

    up
    11
    james dot ellis at gmail dot com
    17 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) :

    local0.info /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
    etc

    saves disk space among other things - more at "man syslog.conf"
    up
    6
    stevekamerman at gmail dot com
    6 years ago
    This function sends messages in BSD Syslog RFC 3164 format (https://tools.ietf.org/html/rfc3164).

    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:

    <?php
    syslog    (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
    up
    5
    OWM
    4 years ago
    Syslog autodetects newline control characters and therefore splits the message by multiple lines. To prevent this behavior in PHP 7.3+ you can use undocumented (at this moment) ini setting:

    <?php

    ini_set    ('syslog.filter', 'raw');

    # more info here: https://bugs.php.net/bug.php?id=77913
    up
    8
    Antonio Lobato
    14 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:

    <?php
    openlog    ("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.
    up
    3
    rgagnon24 at gmail dot com
    6 years ago
    This one had me going for a while when using LOG_ constants in another object, when developing on Windows, but deploying on Linux.

    Windows evaluates some of the LOG_ constants to the same value, while LINUX does not.

    The 8 constants and their differences on the platforms to be aware of:

    Linux has these values as:
    ========================
    LOG_EMERG = 0
    LOG_ALERT = 1
    LOG_CRIT = 2
    LOG_ERR = 3
    LOG_WARNING = 4
    LOG_NOTICE = 5
    LOG_INFO = 6
    LOG_DEBUG = 7

    While on Windows, you have:
    ==========================
    LOG_EMERG = 1
    LOG_ALERT = 1
    LOG_CRIT = 1
    LOG_ERR = 4
    LOG_WARNING = 5
    LOG_NOTICE = 6
    LOG_INFO = 6
    LOG_DEBUG = 6

    So if you're setting LOG_WARNING in your code, Linux will use 4 as the priority while Windows will use 5.

    This is not a bug in PHP on either platform, but a difference in the system header files that PHP compiles with. Not really anything you can do, but be aware if you're wondering why your messages log at different priorities depending on the platform, this could be why.
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    2
    huangyg11 at gmail dot com
    9 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");
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    2
    helly at php dot net
    17 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); };
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    0
    Anonymous
    3 years ago
    There's no point to manually timestamp the message (as shown in docs' example) as all sane logging systems timestamp all entries by themselves.
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