You need to have the oracle client installed on your system.
And you need to read bugs-dos-and-donts BEFORE you submit
any 'bug' reports.

--Jani

I'm sorry to say this, but I have a complete ORACLE-Installation (Client, Development, Administration), instead other Applications won't run and I have to administrate our ORACLE Installations. The Do's and Don'ts says nothing about missing PHP-Files like PHP_OCI8.DLL within the distribution of the WIndows Installer for IIS. This File won't come with ORACLE.
After some looks I'm missing other PHP_*.DLL's within this distribution, too.
Where can I get these files for the PHP.EXE in this distribution. As you can see below, the other DLL's (Windows Distribution CGI - Apache) won't work with this PHP.EXE

I'm sorry to say this, but if the dll is there as you say it is, and you still get that message, then that means your Oracle install isn't all that well. It requires some Oracle dlls in the %PATH%, and it's your responsibility to have them properly installed.

But why worls my other Applications whcih are using OCI, too. It seems more to be a compile/linking error. Because it happens on the first call of the DLL. Are there any differences between the both Binaries (IIS and CGI/Apache)? I saw, that thy have the same date, bit not the same time.
And where are the DLL's for the IIS Shipment? There are no DLL's within the ZIP-File. (The File's only 738 K). I've tested the same with the other DLL's out of the CGI-Shipment together IIS PHP.EXE
Here I have the same calling Problemm i.e. PHP_LDAP.DLL, PHP_MSSQL.DLL, PHP_PRINTER.DLL. I have a complete MS SQL-Workbench on my machine, too. 
I don't think it's a PATH-Problem
Here's the complete PATH from my machine:

%SystemRoot%\system32;%SystemRoot%;%SystemRoot%\System32\Wbem;C:\Oracle\Ora81\bin;C:\Program Files\Oracle\jre\1.1.7\bin;C:\PROGRA~1\COMMON~1\RandSync\TRANSL~1\LtNts4\;C:\Oracle\Ora81\orb\bin;C:\MYSQL\BIN;C:\PHP;C:\PHP\DLL;C:\PHP\EXTENSIONS;

And the ORACLE-Settings are standard.

which of the directories in your %PATH% contains oci.dll?

The OCI.DLL is within C:\Oracle\Ora81\bin; 
which is in the PATH

could you try opening php_oci8.dll in Dependency Walker (http://www.dependencywalker.com/)? does it report any problems?

I'm not very familiar with the Dependency Walker. As far as I can see, there are no errors logged. But I can send you the DWI-File if you want to see the Image.

Does PHP work if you disable every extension?
If so, try enabling ONLY this extension:

php_exif.dll  (it definately doesn't need any extra libs)

If it works, then try enabling php_oci8.dll too.
btw. What is your extension_dir line in php.ini?

--Jani

Hello Jani,

I've tried as recommended the PHP_EXIF.DLL and and there comes an error, too. PHP without any extensions works without no problems.

The Line within PHP.INI looks like:

; Directory in which the loadable extensions (modules) reside.
extension_dir = "C:\PHP\extensions\"

For me it looks like the PHP.EXE from the distribution IIS (without DLL's in the package) won't fit with the DLL's from the 2nd distribution for Apache. Both for Windows.

What does phpinfo() output for extension_dir ??

--Jani

And also, where are the extensions located?
Are they in C:\php\extensions\ ???

Hello Jani,

the DLL's are really in this Path and .phpinfo() shows

Directive     Local Value        Master Value
...
extension_dir E:\PHP\extensions\ E:\PHP\extensions\ 

If extension_dir points to drive E: and the extensions
are on drive C: I can't understand how it could work..

Also, the error message points to totally different place.
So what's the correct one??

No feedback and seems to be user error anyway.