The constants below are always available as part of the PHP core.
| 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 | 
| Constant | Description | 
|---|---|
| LOG_AUTH | security/authorization messages (use LOG_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 | 
| 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 | 
| Constant | Description | 
|---|---|
| DNS_A | IPv4 Address Resource | 
| 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_ALLinstead. | 
| DNS_AAAA | IPv6 Address Resource | 
| DNS_ALL | Iteratively query the name server for each available record type. |