== Problem
Consider the following from an httpd.conf file...
LoadModule php5_module "E:/xyz/php/php5apache2_2.dll"
PHPIniDir "E:/xyz/php"
...which led to the dreaded...
PHP Warning: PHP Startup: Unable to load dynamic library 'E:\\xyz\\php\\ext\\php_mysql.dll' - The specified module could not be found.
Note, however, that PHP.exe apparently was found and executed php pages in Apache, but the MySQL functions therein failed.
== Solution
Because PHP dir was not in $PATH, php5apache2_2.dll failed to find php_mysql.dll (the only extension I enabled) during Apache 2.2 start.
== Caveat (!)
The BIG issue is that, setting $PATH in...
<desk icon>My Computer
<rt click>Properties
<tab>Advanced
<button>Environment Variables
...didn't export the $PATH change such that restarting the Apache service (in MMC) would pick it up. So I tested the working solution (adding PHP dir to $PATH), but it failed because of HOW I set it. It succeeded only when I REBOOTED after changing the $PATH. There may be an easier way that this, but I do not know it at present.
== Comment
Consider whether PHP dir should need to be in $PATH at all, when PHP.exe apparently was found and executes php pages in Apache, but php5apache2_2.dll failed to find whatever was needed to load the extensions. This should perhaps be addressed.
Note that on a WAMP installation (W2K,Apache,MySQL,PHP), only PHP is required in $PATH.