For some putting "' around the path has helped.. 
And terminate it with a \ 

I put 

extension_dir = "c:\php\extensions\"

and now the error is:

Unable to load dynamic library 'c:\php\extensions\php_oci8.dll'

the file php_oci8.dll exist in c:\php\extensions\

to look on which external dlls an exe or an dll is relying you can use the dependency walker - 
http://www.dependencywalker.com/

I don't understand this program.
Please check this image :

http://www.netred.cl/php.jpg

(image of my screen).

Sniper,

I change my php.ini 

I comment php_oci8.dll
and uncomment php_oracle.dll

This work.

But now I recieve the following problem:

TNS:could not resolve service name 

I try with 

$db= ora_logon("demo_user/demo_password@demo","");

This TNS exist and the user and the password too.

(this is the right place for this question?)

thank you again.

I found in the faqs the following (exactly the same problem)

"This problem was also seen under the ODBC drivers for Windows.  The solution so far has
been to remove all Windows based carriage returns (\r\n) in your TNSNames.ora and
SQLNet.ora file, and replace them with unix style carriage returns (\n).

This should end your problem.  Why is this happening?  It's unknown at the time, but is
being investigated.  
"

I convert this 2 files to Unix format (only \n) but the problem still happend.

any help?

sorry.... ORACLE VERSION 8.05

Ask support questions on the appropriate mailing list:

http://www.php.net/support.php

( php-db / php-windows ) after you have searched the
archives, of course.

--Jani

I have same problem with Unable to load dynamic library 'c:\php\extensions/php_oci8.dll'

What is sollution ?

you need to have the oracle client installed on both machine
and your may not have uncommented php_oci8.dll and php_oracle.dll, only one a the same time if not you will have a problem...
and "extensions_dir:./extensions" 
nothing else

bye

I have same problem with Unable to load dynamic library
'c:\php\extensions/php_oci8.dll'

   I've tried fixing this problem so many times but I haven't got any good result!
   How can I solve it!