Getting metabox value within a shortcode?

$post is outside the scope of your shortcode function, you have to globalize it first:

global $post;
$sidebar = get_post_meta($post->ID, 'metabox_sidebar', true);

Related Posts:

  1. WordPress global variables?
  2. Form submit from modal window to parent window
  3. Add a Meta Box for uploading a SECOND Featured Image?
  4. Remove the Yoast SEO Post Metabox [closed]
  5. Sample code for validating custom metabox?
  6. One metabox for multiple post types
  7. How to add a class to meta box
  8. Has anyone successfully integrated qtranslate with custom metaboxes?
  9. Add Meta box Befoure Post Title
  10. Editing Screen: Make Update or Publish Button Follow The Page
  11. Why can’t I hook into save_posts after admin_init?
  12. Meta Boxes in Front End Post Submission Form
  13. Remove a plugin meta box from the dashboard
  14. Custom meta box shown when template is chosen [duplicate]
  15. Modifying the main editor priority
  16. How to make a meta box field a requirement
  17. Adding uploaded images to editor from metabox instead of default popup uploader
  18. Choosing a default page tempate (Classic => Gutenberg)
  19. How to remove the RichText Meta Box
  20. wp_editor in add_meta_boxes does not show gallery
  21. Replace the Post Excerpt Meta Box with a Field in My Custom Meta Box
  22. Add character count to custom metabox
  23. Update caption for metabox gallery images
  24. How to show post format gallery metabox image caption in the post front end
  25. datetime_timestamp shows numbers only? need in date and time
  26. Remove a metabox registered by another plugin – Woocommerce [closed]
  27. Custom Metabox with Ajax in Edit Post – Stuck
  28. Possible to limit custom meta boxes depending on what page template is used?
  29. Post.php – Conditional statements for new post and edit post
  30. How to generate a featured image from a video embeded in a metabox
  31. Meta box io oembed returns list not array
  32. Add Slug Metabox to posts for contributors
  33. How to verify meta box is registered in Unit Testing?
  34. Add a custom field to top attribute in WooCommerce
  35. wp_editor in metabox not working
  36. Select box saves but doesn’t update value in admin
  37. How to get meta box values – WP tuts tutorial
  38. retrieve meta key when checkbox is used
  39. Add Meta Box not showing on New Post – Custom meta box not showing
  40. add wp_editor to custom_meta_box
  41. Customize WordPress Media Upload and New Media Manager Menu in add post Metabox
  42. How to display a custom post type’s media library inline on meta box
  43. Modules with meta box implementations
  44. Remove meta box for specific page
  45. How To Add Custom Meta PDF Upload Box to WooCommerce Products (and post link on frontend)
  46. Using WYSIWYG In custom meta boxes
  47. Visual/Text tabs in wp editor Not Showing
  48. save_post action to include wp_insert_post_data filter, gathering meta field info & prevent infinite loop
  49. Show Meta Box On Specific Page Template
  50. Change the context of excerpt metabox for the ‘New Post’ page
  51. How to have meta boxes save via REST in Gutenberg?
  52. Show preview of post changes on page
  53. Add Metabox to settings / options page
  54. Undefined index error in custom post metabox
  55. WPAlchemy MediaAccess inserting media link in WP Editor instead of custom field in metabox [closed]
  56. Meta Box will not display
  57. How to get the meta box name and value
  58. My custom write panels won’t save data. What am I missing?
  59. meta box & callback function
  60. $_GET & $post_ID
  61. How can i use this meta box function in my template ? (WordPress)
  62. How to disable Author dropdown in Gutenberg’s Status and Visibility panel
  63. get_post_meta as a list for drop down search filter
  64. add_post_meta | update_post_meta | Via the frontend
  65. Why does not my metabox save?
  66. Display stored value in Meta Box
  67. Display Content if custom meta box checkbox is checked
  68. How to add meta box for current post format?
  69. How to check specific value in two metabox?
  70. How to show taxonomy terms from wordpress database?
  71. Error showing in current page id in wordpress admin
  72. Show value of select dropdown in meta box
  73. Output list from each line of metabox (shortcode)
  74. Hybrid meta box, how to show?
  75. Understanding WordPress’ post type support
  76. How to make a metabox that contains link categories?
  77. Include doesn’t work, getting strange path: (/usr/local/php53/lib/php) – Whats wrong? (WPAlchemy)
  78. wordpress alchemy put custom metabox on certain page only
  79. using WPalchemy to output custom metabox from homepage template
  80. meta box pop up upload button wont work
  81. How to Edit & Update meta_box values from Front-End user Form
  82. Custom meta box in editor of custom post type not working
  83. Custom fields changes the formatting of metabox input
  84. Is this Edit Post Screen?
  85. Meta Box – Javascript Datatable
  86. Metabox on a custom page – How to include the appropriate default scripts and styles?
  87. custom metabox nonce verification fails
  88. Extensible add_meta_box with apply filters
  89. Generating image sizes when uploading through wp.media
  90. Add “Select” For Custom Post Type Metabox
  91. Set post title to same value as a tow meta box
  92. add_post_meta Adds post meta but the value is blank
  93. Best practices for meta box placement?
  94. Echo order box (in pages)
  95. Tags meta box don’t show when creating a new post type
  96. Remove duplicated values from meta box values
  97. Remove Title, Editor and Meta Box Support Based on Post Formats
  98. Custom select box meta field
  99. Saving an upload media meta box field
  100. My meta box don’t want to save value
Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)