Thanks this was a great help and it works out.
I want to share the solution:
* Go to the WordPress Source Viewer to default theme in the search.php -file (http://phpxref.com/xref/wordpress/nav.html?_constants/index.html)
* You can see if you like to want to put an URL into a php function use: "functionname(TEMPLATEPATH./'filenameinthetemplatedirevtory.xyz');"
* If you like to put the filename as a Variable like you need it for a filepointer use:
$filepointer = fopen($myfilevariable, "r");"
Ok, hope this helps other hobby coders as well - this cost me some time.