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 (use`LOG_AUTHPRIV`instead 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:
<?php
$facilities = array(
  LOG_AUTH,
  LOG_AUTHPRIV,
  LOG_CRON,
  LOG_DAEMON,
  LOG_KERN,
  LOG_LOCAL0,
  LOG_LPR,
  LOG_MAIL,
  LOG_NEWS,
  LOG_SYSLOG,
  LOG_USER,
  LOG_UUCP,
);
for ($i = 0; $i < 10000; $i++) {
  foreach ($facilities as $facility) {
    openlog('test', LOG_PID, $facility);
    syslog(LOG_ERR, "This is a test: " . memory_get_usage(true));
  }
}
?>