I just installed PHP and Apache on my home PC. When I try to call function
fatal error: call to undefined function mysql_connect.
extension_dir = "C:\php\ext"
After looking at your
phpinfo() output, it appears the mysql extensions are not being loaded. I suspect you might be editing the wrong php.ini file (there might be multiple copies). Make sure you are editing the php file at C:\php\php.ini (also check to make sure there is no second copy in C:\Windows).
Also, you should check your Apache logs for errors (should be in the \logs\ directory in your Apache install.
If you haven't read the below, I would take a look at the comments section, because it seems like a lot of people experience quirks with setting this up. A few commenters offer solutions they used to get it working.
Another common solution seems to be to copy libmysql.dll and php_mysql.dll from c:\PHP to C:\Windows\System32.