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(PHP 4, PHP 5)



bool syslog ( int $priority , string $message )

syslog() はシステムログが出力するログメッセージを生成します。

ユーザー定義のログハンドラの設定に関する情報については、Unix マニュアルの syslog.conf (5) を参照ください。 syslog の facility と option に関するより詳細な情報は、 Unix マシンの syslog (3) にあります。



priority は、容易さ (facility) とレベル (level) の組み合わせです。以下の値が使用できます。

syslog() の優先順位 (降順)
定数 説明
LOG_EMERG システムは使用不可
LOG_ALERT アクションを直ちにおこす必要がある
LOG_CRIT 致命的な条件
LOG_ERR エラーを発生する条件
LOG_WARNING 警告を発生する条件
LOG_NOTICE 通常の動作だが、特徴的な条件
LOG_INFO 情報を与えるメッセージ
LOG_DEBUG デバッグ用のメッセージ


残りの引数は送信するメッセージです。ただし、文字 %m は、errno の値に対応するエラーメッセージ文字列 (strerror) に置換されます。


成功した場合に TRUE を、失敗した場合に FALSE を返します。

例1 syslog() の使用例

// syslogをオープンし、プロセスIDをインクルードし、標準エラー出力にも
// ログを出力します。そして、ユーザー定義のログ記録機構を使用します。
openlog("myScriptLog"LOG_PID LOG_PERRORLOG_LOCAL0);

// 何らかのコード

if (authorized_client()) {
// 何かをする
} else {
// クライアントは未認証!
    // ログを記録する
$access date("Y/m/d H:i:s");
syslog(LOG_WARNING"Unauthorized client: $access {$_SERVER['REMOTE_ADDR']} ({$_SERVER['HTTP_USER_AGENT']})");



Windows NT では、syslog サービスはイベントログを使用してエミュレートされます。


Windows 環境では、openlog()facility パラメータに LOG_LOCAL0 から LOG_LOCAL7 までを使用することはできません。


  • openlog() - システムのロガーへの接続をオープンする
  • closelog() - システムログへの接続を閉じる

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User Contributed Notes 14 notes

Antonio Lobato
5 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.
james dot ellis at gmail dot com
7 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"
nospam \100 jraxis com (that's right!)
13 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.
helly at php dot net
8 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); };
daniele dot patoner at biblio dot unitn dot it
11 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");

mavetju at chello dot nl
14 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:
bb at lb-data dot co dot at
15 years ago
In Windows NT, use the following values of priority:
1 = error,
6 = info
rcgraves+php at brandeis dot edu
15 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.
huangyg11 at gmail dot com
1 month 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");
gregj at pdxperts dot com
11 years ago
The message string sent to the log file is limited to 500 characters.
dpreece at paradise dot net dot nz
13 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
11 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
8 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
14 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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