You could try to use apache2-mod-php5.tcz instead of php5.tcz. This should enable php automatically when no other special changes are made to httpd.conf. php5.tcz is not including the php module for apache2, only the interpreter, so you cannot LoadModule it. However you could of course also "cgi" it like every other script interpreter, but then you need the cgi configuration for apache2, not the php5 module configuration.