Grabbing the first image attached to a post and use it with the admin columns

Question

I'm currently using @kovshenin's tutorial here on adding a thumbnail (a featured image) to my post type admin columns.

Would it perhaps be possible ( and how :) ) to retrieve the first image attached to a post first, if no featured image available? (and perhaps return a local hosted image if also no featured image available)

This is the code I currently have:

add_action( 'after_setup_theme', 'cor_after_setup_theme' );
function cor_after_setup_theme() {
  add_image_size( 'edit-screen-thumbnail', 48, 48, true );
}

add_filter( 'manage_edit-product_columns', 'cor_add_product_column', 10, 1 );
function cor_add_product_column( $column ) {
  $column_thumbnail = array(
    'thumbnail' => ''
  );
  $column = array_slice( $column, 0, 1, true ) + $column_thumbnail + array_slice( $column, 1, NULL, true );
  return $column;
}

add_action( 'manage_posts_custom_column', 'cor_manage_product_column', 10, 1 );
function cor_manage_product_column( $column ) {
  global $post;
  switch ( $column ) {
    case 'thumbnail':
      echo get_the_post_thumbnail( $post->ID, 'edit-screen-thumbnail' );
      break;
  }
}

Edit:

As mentioned in the next comments, it took some time to figure things out :). In the end, and with the suggestions of @ifdion I came up with the next result:

add_action( 'after_setup_theme', 'cor_after_setup_theme' );
function cor_after_setup_theme() {
  add_image_size( 'edit-screen-thumbnail', 48, 48, true );
}

add_filter( 'manage_edit-product_columns', 'cor_add_product_column', 10, 1 );
function cor_add_product_column( $column ) {
  $column_thumbnail = array(
    'thumbnail' => ''
  );
  $column = array_slice( $column, 0, 1, true ) + $column_thumbnail + array_slice( $column, 1, NULL, true );
  return $column;
}

add_action( 'manage_posts_custom_column', 'cor_manage_product_column', 10, 1 );
function cor_manage_product_column( $column ) {
  global $post;

  $args = array(
    'numberposts' => 1,
    'post_mime_type' => 'image',
    'post_parent' => $post->ID,
    'post_type' => 'attachment',
  );
  $attachments = get_children( $args );

  if ( has_post_thumbnail() ) {
    echo get_the_post_thumbnail( $post->ID, 'edit-screen-thumbnail' );

  } elseif ( $attachments ) {
    foreach ( $attachments as $attachment ) {
      $image_attributes = wp_get_attachment_image_src( $attachment->ID, 'edit-screen-thumbnail' );
      echo '<img src="' . $image_attributes[0] . '">';
    }

  } else {
    echo '<img src="' . plugins_url( '/img/edit-screen-thumbnail.png', __FILE__ ) . '">';
  }
}

Another edit

Not entirely sure if this grabs the last image attached to a post, but anyways, this code will get it:

add_action( 'after_setup_theme', 'cor_after_setup_theme' );
function cor_after_setup_theme() {
  add_image_size( 'edit-screen-thumbnail', 48, 48, true );
}

add_filter( 'manage_edit-product_columns', 'cor_add_product_column', 10, 1 );
function cor_add_product_column( $column ) {
  $column_thumbnail = array(
    'thumbnail' => ''
  );
  $column = array_slice( $column, 0, 1, true ) + $column_thumbnail + array_slice( $column, 1, NULL, true );
  return $column;
}

add_action( 'manage_posts_custom_column', 'cor_manage_product_column', 10, 1 );
function cor_manage_product_column( $column ) {
  global $post;

  $args = array(
    'numberposts' => 1,
    'post_mime_type' => 'image',
    'post_parent' => $post->ID,
    'post_type' => 'attachment',
    'post_status' => null,
  );
  $attachments = get_posts( $args );

  if ( has_post_thumbnail() ) {
    echo get_the_post_thumbnail( $post->ID, 'edit-screen-thumbnail' );

  } elseif ( $attachments ) {
    foreach ( $attachments as $attachment ) {
      echo wp_get_attachment_image( $attachment->ID, 'edit-screen-thumbnail' );
    }

  } else {
    echo '<img src="' . plugins_url( '/img/edit-screen-thumbnail.png', __FILE__ ) . '">';
  }
}

Answer 1

Yes it is possible. I believe it is better if you put it in a conditional statement

1. Check for featured image easy;
2. Check for attached file with an image mime type using this and this;
3. Check for any <img> tag in the post content (detail);
4. If there is no image at all, then use a default image

Hope this help