0bc47397_e_DNS_resolver_library_for_PHP__value
[key name] expire [type] DNS_RECORDTYPE_SOA [value] 
An integer value that specifies in seconds the period during which the slave server sees the zone information is valid. After the expiry, the server will stop sending any records of the zone in response to the queries until the entire zone information is updated.
"PHPresolver" - a simple DNS resolver library for PHP
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