PHP Manual . ... PHP 3 <= 3.0.18, PHP 4 >= 4.0.0) checkdnsrr -- Check DNS records corresponding to a given Internet host name or IP address . int checkdnsrr ( string host [, string type]) . Searches DNS for records of type type corresponding to host . Returns TRUE if any records are found; returns FALSE if no records were found or if an error occurred. type may be any one of: A, MX, NS, SOA, PTR, CNAME, or ANY. ... Host may either be the IP address in dotted-quad notation or the host name. ...