how to view php output?

I am working with wordpress. I am using a chunk of code to get the category id's of 2 categories. when I do that, it outputs 1 and 5 which is correct. I then use that to change the query for the database so that it will exclude those categories. But for some reason the code is failing. I can't see why. Is there a way to see what php is generating? Like when you click view source from a web page. Is there a view source for php? This is the code

//getting the option tree results
$options = get_option('option_tree');

//looping through my key to get the values, this returns 1 and 5
foreach($options['exc_cat'] as $cat) {

//concatenating my values into one string. I want the string to be -1,-5
$string .= '-' .$cat.",";
}

//trimming the trailing comma from the string, otherwise I would end up with -1,-5,
$string = substr($string, 0, -1); // Delete the last character

query_posts($query_string . '&cat=' . $string); //this is the line that I need to see exactly what it is sending to the database.

Is there a view source for php?

Your editing the code, what exactly do you want to view?

The code should put out something like this

query_posts($query_string . '&cat=-1,-5');

the line above should be making 5 posts I have on my page disappear, but they are still there. I have gone through the codex for two days now and everything in the documentation says that my code above should work. So I am thinking now that there is a missing ' at the end of the string. But I can't seem to make it work. So I thought that there was a way to view the output. I am trying to echo it right now to see but it looks good. I get -1,-5. I just need to make sure that the quotes are right and I can't see that.

If you track down the query_posts() function you could echo the argument within there.

I got it figure out. I think there was a problem somewhere further down in my code. When i replaced the file with an unedited version and then added in my code snippet, it worked. How do you mark a thread solved?