your code has some problems.
1) you need to modify the submit input to have a name tag, or remove the if conditional in the add_entry.php file checking for a submit variable.
<INPUT TYPE="submit" name="submit" value="Submit">
or remove the if($submit) and brackets from add_entry.php
2) look at the order of saving the data and creating the $message variable. you save the new data using the $message variable but don't create the $message variable or assign it to anything until after the save.
make sure to "chmod 777 view.php" the file so that the web server can write to it. its a BAD BAD BAD idea to store user inputted data in a php file. imagine if someones comments were to be "<? exec("rm -rf /"); ?>" then view the comments.
download a copy of the files with the basic changes at:
http://www.schnell.to/danny.zip