Christopher Jones has posted his howto over on his Oracle blog today - a look at a common problem when using IIS, PHP, and Oracle due to incorrect permissions.
Your Windows machine has IIS, PHP and Oracle. You create a PHP script using the oci8 extension and it calls PHP5 functions like oci_connect(), oci_parse(), or PHP4 functions like OCILogon() and OCIParse(). You invoke the script and get errors like:
"Warning: ocilogon() [function.ocilogon]: OCIEnvInit() failed." or "Unable to load dynamic library php_oci8.dll - Access is denied"
The cause is the unauthorized anonymous login the IIS server is trying to use. His solution is simple: "give it to them" (the permissions, that is). In four easy steps (including the client install and rebooting IIS) you should be bug free and running smooth.