Grab one attachment of a given kind

<?php
/*
 * WordPress Function
 * Drop in your functions.php, or create a simple plugin (and drop all your functions there)
 * Parameter $idi : the $post-ID
 * Parameter $type : A full or partial mime-type, e.g. image, video, video/mp4, application/pdf
 * Usage : <a href="<?php echo getAttach($post->ID,'video'); ?>">download video</a>
 */

function getAttach($idi,$type)
{
    $empty = "no attach...";
    if ( $files = get_children(array(   //do only if there are attachments
     'post_parent' => $idi,
     'post_type' => 'attachment',
     'numberposts' => 1,
     'post_mime_type' => $type,
     'order' => 'ASC',
     'orderby' => 'menu_order'
     ))){
         foreach( $files as $file ){ // only run once, as numberposts = 1
            $file_link = wp_get_attachment_url($file->ID);    //get the url for linkage
          }
          return $file_link;
    }
    else
    {
        return $empty;
    }
}
?>