looks like it is not finding your file.. did you create a file there first?
this looks kinda wrong
$fp = fopen ("home/httpd/html/log.txt", "r");
do you know the full path to the file?
$fp = fopen ("/usr/home/httpd/html/log.txt", "r");
you will want to specify the full path..
or if your web server is located in..
/var/www/apache/ht-doc/httpd/html/
or somthing like that, it doesnt have to be like the one above but all you need to so is make a file called log.txt in the directory were you php script is
then do this
$fp = fopen ("log.txt", "r");