Display (this) Based on Multiple Cat IDs from User Input (widget options)

Hi,

I’ve been searching high and low for how to do this for hours to no avail.

I’m coding a plugin where my goal is to allow someone to place “whatever” on single posts based on category id’s that they specify.

Scenario
————
Place Google Adsense on post of these categories:

In the widget options I provide a field to define category id’s (comma separated):

<!-- Multiple Category ID's -->
      <p>     

        <?php echo '<label for="' . $this->get_field_name('gaw_placebymcat') . '">' . __(' Multiple Categories by ID:') . '
        <input style="width:25%;" id="' . $this->get_field_id('gaw_placebymcat') . '" name="' . $this->get_field_name('gaw_placebymcat') . '"
        type="text" value="' . $gaw_placebymcat . '" /></label>'; ?>

      </p>

So lets say their input is 6,11,17 – the person would want the widget (adsense ads) to display on all post in the categories 6,11, and 17.

So I got the conditional tag in_category to correct return true or false based on the current posts categories by hard-coding the array as normal:

if (in_category( array( '6', '11', '17' ) ) ) { echo 'display ads her because this is cat 6, 11 or 17';} else {echo 'we wont display because condition is false';}

So I confirmed this as working. So it looks like I need an array like in the code above. So I looked how to create an array from a comma separated string and came up with this:

$multicats = $gaw_placebymcat;
//the variable is user defined cats sep'd by commas

// split to array
$multicatarray = explode(', ', $multicats);
print_r($multicatarray);

The result:
Array ( [0] => 6,11 )

But I don’t think this what I want, and I have know idea how to incorporate that into the in_category condition. Again, I’m pretty new to PHP and a bit of a hack I guess that’s how you learn ??

Anyway, I’m so hard-headed I worked on this for 8 hours before asking here.

Hope one of you can point in the right direction. Maybe I’m totally turned around here.

So please, please help me!

Thanks a bunch,
Bryan