When transferring a domain name to us or when updating your DNS servers for the domain, your local computer DNS servers might be still resolving your old site IP address, which will lead to either you not being able to access your new site or you accessing the site hosted with your previous hosting company.
Usually after certain period of time (24-72 hours) your local computer will naturally start to resolve your new site IP, and you will start seeing your site hosted with us (instead of your old provider).
Using DNS_ALL fails on some domains where DNS_ANY works.
I noticed the function getting stuck on the DNS_PTR record, which caused it to return FALSE with this error: PHP Warning: dns_get_record(): res_nsend() failed in ....
This gets all records except DNS_PTR: When I use DNS_ALL as the second parameter to invoke dns_get_record() on the OS of Windows, PHP emits a warning with the message "Warning: dns_get_record(): Type '251721779' not supported in on line blah", and DNS_ANY is always OKAY.
Please note that Firewalls and anti malware software detects (and depending on company policies even blocks) DNS_ANY requests. This is because DNS_ANY requests can be exploited for creating "amplification (D)DOS attackes": You send 1 DNS_ANY request and get a huge amount of information back, thus even small requests can result into hugh network load.
Please, note that some distributions by default do not install DNS caching service, so flushing the DNS cache might not be required or possible without further package manipulation.
Even though my DNS is automatically updated when it changes, via the highly versatile ddclient package, the traditional dynamic DNS update protocols (including dyndns.org's) are typically site-specific and non-standard.
While googling around for a better solution, a friend on IRC pointing me to a utility that has been around since BIND 8: nsupdate.
For Windows XP: Close all Internet applications that you are using, such as email client, and web browsers. Enter in the text field, the command "cmd" and hit ENTER (Select OK).
In the new black window enter ipconfig /flushdns and then hit the ENTER button on your keyboard.