The behaviour of these functions is affected by settings in php.ini.
For further details and definition of the PHP_INI_* constants see ini_set().
Here is a short explanation of the configuration directives.
Whether or not to define the various syslog variables (e.g. $LOG_PID, $LOG_CRON, etc.). Turning it off is a good idea performance-wise. At runtime, you can define these variables by calling define_syslog_variables().
The constants below are always available as part of the PHP core.
Table 2. 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 | 
Table 3. 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 | 
Table 4. dns_get_record() Options
| 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 RFC 1010 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 | Itteratively query the name server for each available record type. |