Everything works fine..
Check if you don't have any old dlls in Windows dirs (C:\windows and C:\windows\system32).
Also, if you have mysal installed, with its dir in the path, check the version of its libmysql.dll file, because it may be causing the problem.

If still doesn't work, read *carefully* the on-line manual: http://php.net/install.windows.manual

here is the exact thing i did when i tried to upgrade:

stopped server, moved all php files that were in c:\php5\ into c:\php5\old\, extracted all files from the zip file to c:\php5\. renamed the php-dist.ini to php.ini and configured each setting as needed, including open_basedir, extension_dir, uncommented the php_mysql.dll and php_gd2.dll files, and other non important things which i know for a fact are not causing an error.

copie php5apache2.dll and php5ts.dll to c:\program files\apache group\apache2\, as well as the new php.ini file. no files relating to php are/were in c:\windows\system32 folder, so there wasnt a problem there.

started server, and i got these errors in the error.log:

PHP Warning:  PHP Startup: Unable to load dynamic library 'C:\\php5\\ext\\php_gd2.dll' - The specified module could not be found.\r\n in Unknown on line 0
PHP Warning:  PHP Startup: Unable to load dynamic library 'C:\\php5\\ext\\php_mysql.dll' - The specified module could not be found.\r\n in Unknown on line 0

although i verified that these files were infact there, and i made certain that i reapplied all file permissions oh subfolders and files, so apache infact should have had access to them.

all mysql related pages failed to load, and all non related ones worked.

tried replacing the two previously mentioned dll files with the older versions, didnt work. overwrote all old files ontop of all new files including the ones in the apache folder, worked. tried overwriting the new dll's overtop of the old dll's, didnt work. restored the old ones, worked.

only when every last file present in the php and apache folders was of the 5.0.2 version did anything work.

verified all directives in the php files several times, verified file permissions serveral times, verified file locations and versions several times.

i cannot perceive any logical explanation other than some problem in the php install files, but it doesnt make sense that they only dont work for me, so i am going to re-try this entire thing again tonight.

i tried this again today.

i moved all 5.0.2 files in c:\php5\ to a subfolder, and extracted the new 5.1.2 files in their place. i then copied php5apache2.dll and php5ts.dll to the apache folder, overwriting the older ones from php 5.0.2

i verified my configuration of the php.ini file, and although the extension_dir, open_basedir, and extension=php_mysql.dll lines were set up properly, and system environment variables were already in place due to the previous version of php, WHICH WORKED, by the way, yet when i load my front page, nothing happens, because the content is built after some mysql queries are attempted.

i then kept the php 5.1.2 config file, and replaced only the php5ts.dll and php5apache2.dll files in the apache config, and all files in the c:\php5\ folder, with the original files, and poof! everything worked once again.

so, i know the php.ini file works then, since it worked on one version and not with the other, and the older version works perfectly fine in every single way (even works with the php.ini file of a higher up version too), which leads me to the inescapable conclusion that the combination of the extracted files from the php 5.1.2 archive do not work on my system, whereas the php 5.0.2 files do. this means it is not my system to blame, not my config to blame, not php 5.0.2 to blame.

something has been changed between versions that makes it impossible to access my mysql server thru my apache server.

environment:

-Microsoft Windows XP [Version 5.1.2600] (Professional)
-MySQL Server 4.18
-Apache HTTP Server 2.0.55
-php 5.0.2 / php 5.1.2

the only php-addon i install is PEAR, the version that comes with 5.0.2 i install on 5.0.2, and the version that comes with 5.1.2 i install with 5.1.2

i dont even use PEAR really, all i use is what ive stated above, everything else i run is php scripts made by me that in no way affect the settings of php, apache, or mysql, they just use them.

i would really, really, really like to know how to get around this issue, because id like access to all the latest bugfixes and all that good stuff.

EDIT: my current PHP version is actually 5.0.4, now 5.0.2, not that it matters.

if someone thinks it may be a good idea to check what other versions above my current one i can use, then ill try it tomorrow, and get back to you on what versions i can successfully install.

Sorry, but your problem does not imply a bug in PHP itself.  For a
list of more appropriate places to ask for help using PHP, please
visit http://www.php.net/support.php as this bug system is not the
appropriate forum for asking support questions.  Due to the volume
of reports we can not explain in detail here why your report is not
a bug.  The support channels will be able to provide an explanation
for you.

Thank you for your interest in PHP.