Open PHP result in a php echo code

Hello,

guys you are so fantastic. Maybe you know a solution for this problem…

I am using the following code to read out the meta field named “GalleryID”.

<?php

function meta_galleryid() {
       global $id, $post_meta_cache;

        if ( $keys = get_post_custom_keys() ) {
                foreach ( $keys as $key ) {
                        $values = array_map('trim', get_post_custom_values($key));
                        $value = implode($values,', ');
                        if ( $key == 'GalleryID' ) {
                                echo "$value";
                        }
                }
        }
}
?>

This works fine. The result is for example “1” or “2” if I enter these numbers in the meta field.

I am using the NextGEN Gallery and by using the code <?php echo nggshowgallery(1,450,450); ?> the gallery with the ID 1 opens. I want to connect now this NEXTGen-Function with the display of the meta galleryID.

I thought that the following code will work:

...
if ( $key == 'GalleryID' ) {
echo "<?php echo nggshowgallery($value,450,450); ?>";
...

But it do not work… Also this do not work:

<?php echo nggshowgallery(<?php meta_galleryid(); ?>,450,450); ?>

Why not? What would be the solution? Is there any possibility to open a php within a php??

Thanks for your help guys
Jen