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预定义常量

下列常量作为 PHP 核心的一部分总是可用的。

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_NOWAIT
LOG_PERROR print log message also to standard error
LOG_PID include PID with each message
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
syslog() Priorities (in descending order)
Constant Description
LOG_EMERG system is unusable
LOG_ALERT action must be taken immediately
LOG_CRIT critical conditions
LOG_ERR error conditions
LOG_WARNING warning conditions
LOG_NOTICE normal, but significant, condition
LOG_INFO informational message
LOG_DEBUG debug-level message
dns_get_record() Options
Constant Description
DNS_A IPv4 Address Resource
DNS_CAA Certification Authority Authorization Resource (available as of PHP 7.0.16 and 7.1.2)
DNS_MX Mail Exchanger Resource
DNS_CNAME Alias (Canonical Name) Resource
DNS_NS Authoritative Name Server Resource
DNS_PTR Pointer Resource
DNS_HINFO Host Info Resource (See IANA's » Operating System Names for the meaning of these values)
DNS_SOA Start of Authority Resource
DNS_TXT Text Resource
DNS_ANY Any Resource Record. On most systems this returns all resource records, however it should not be counted upon for critical uses. Try DNS_ALL instead.
DNS_AAAA IPv6 Address Resource
DNS_ALL Iteratively query the name server for each available record type.

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