Modular installation:
First move or copy php4ts.dll to the windows/system (Windows 9x/Me) or winnt/system32 (Windows NT/2000/XP) directory, overwriting the original existing file; then modify Apache Configuration file httpd.conf: (assuming c:/php/ is your PHP installation path)
LoadModule php4_module c:/php/sapi/php4apache.dll
AddModule mod_php4.c
AddType application/x- httpd-php .php
As CGI installation:
If using CGI mode, please modify the settings of php.ini: cgi.force_redirect = 1 to enhance the security of apache, then insert the following in httpd.conf Content:
ScriptAlias /php/ "c:/php/"
AddType application/x-httpd-php .php
Action application/x-httpd-php "/php/php.exe"
The above are the differences between the two, everything else is the same.