openlog()

(PHP 4, PHP 5, PHP 7)

Open connection to system logger

说明

openlog(string $ident,int $option,int $facility): bool

openlog()opens a connection to the system logger for a program.

The use ofopenlog()is optional. It will automatically be called bysyslog()if necessary, in which case$identwill default toFALSE.

参数

$ident

The string$identis added to each message.

$option

The$optionargument is used to indicate what logging options will be used when generating a log message.

openlog()Options

Constant	Description
LOG_CONS	if there is an error while sending data to the system logger, write directly to the system console
LOG_NDELAY	open the connection to the logger immediately
LOG_ODELAY	(default) delay opening the connection until the first message is logged
LOG_PERROR	print log message also to standard error
LOG_PID	include PID with each message

You can use one or more of these options. When using multiple options you need toORthem, i.e. to open the connection immediately, write to the console and include the PID in each message, you will use:LOG_CONS | LOG_NDELAY | LOG_PID$facility

The$facilityargument is used to specify what type of program is logging the message. This allows you to specify (in your machine's syslog configuration) how messages coming from different facilities will be handled.

openlog()Facilities

Constant	Description
LOG_AUTH	security/authorization messages (useLOG_AUTHPRIVinstead in systems where that constant is defined)
LOG_AUTHPRIV	security/authorization messages (private)
LOG_CRON	clock daemon (cron and at)
LOG_DAEMON	other system daemons
LOG_KERN	kernel messages
LOG_LOCAL0...LOG_LOCAL7	reserved for local use, these are not available in Windows
LOG_LPR	line printer subsystem
LOG_MAIL	mail subsystem
LOG_NEWS	USENET news subsystem
LOG_SYSLOG	messages generated internally by syslogd
LOG_USER	generic user-level messages
LOG_UUCP	UUCP subsystem

Note:

LOG_USERis the only valid log type under Windows operating systems

返回值

成功时返回TRUE，或者在失败时返回FALSE。

参见

• syslog()Generate a system log message
• closelog() 关闭系统日志链接

In second parameter int $option, PI means Process ID (PID).
That is the unique number given to that process. For eg [30326]

To those curious; switching between different facilities is NOT an issue. There is no apparent memory overhead (nor slowdown) by calling openlog multiple(12 * 10000) times.
Shown by this example: 

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