WordPress implode & wp_insert_post question

The second parameter to wp_set_object_terms() takes an array, integer, or string.

(array/int/string)
(required) The slug or id of the term (such as category or tag
IDs), will replace all existing related terms in this taxonomy. To
clear or remove all terms from an object, pass an empty string or
NULL. Integers are interpreted as tag IDs. Warning: some
functions may return term_ids as strings which will be interpreted as
slugs consisting of numeric characters!

You create an array ($cardet["marks"]) but then implode() it. When you implode() it you turn that array into a comma separated string, which wp_set_object_terms() interprets as a single value. wp_set_object_terms() will not break the string on commas and create multiple terms for you, but the solution is simple as you’ve added a step that is breaking things. Remove that step and pass the array to wp_set_object_terms().

if ( isset( $cardet['marks'] ) )
    wp_set_object_terms( $post_id, $cardet["marks"], 'mark' );

There is sample code in the Codex doing exactly this, but with IDs:

// An array of IDs of categories we want this post to have.
$cat_ids = array( 6, 8 );

/*
 * If this was coming from the database or another source, we would need to make sure
 * these where integers:

$cat_ids = array_map( 'intval', $cat_ids );
$cat_ids = array_unique( $cat_ids );

 */

$term_taxonomy_ids = wp_set_object_terms( 42, $cat_ids, 'category' );

If $cardet["marks"] is user supplied data please sanitize it before using it.

Related Posts:

  1. Remove Category description textarea
  2. ACF Custom field not showing in Timber Taxonomy page
  3. Add custom taxonomy fields when creating a new taxonomy
  4. Get value in custom field with taxonomy [closed]
  5. Hide custom field if empty
  6. ACF vs Taxonomies
  7. wp_insert_post not updating custom taxonomy selected if logged in as a subscriber
  8. How to add contents of a custom field to a taxonomy term list?
  9. Search Tool only refreshes Page without showing results
  10. Display value of custom field of custom taxonomy in single post?
  11. How to fetch the data from Advanced Custom post when we search specific keyword or field name related to the post?
  12. Multi-select field for Taxonomy can’t save the value
  13. Filter through custom taxonomy with an array of taxonomy IDs
  14. Loop through custom taxanomy in post and display custom fields from posts
  15. Why do my quick edits for custom taxonomies not show on the post frontend?
  16. new custom filed not showing in taxonomy
  17. Custom field with terms from another taxonomy programmatically
  18. ACF – Can’t get custom post type by taxonomy
  19. Dropdown (with onChange) with custom taxonomies
  20. Register custom taxonomy from a Advenced custom field option page
  21. add custom fields in custom taxonomy meta box in wordpress-3.5.2
  22. Any way to make custom taxonomy field searchable?
  23. How do I create a term for every value of a post meta?
  24. How to add images to taxonomies?
  25. Can you add the visual editor to the description field for custom taxonomies?
  26. Is there a way to disable a term rather than deleting it?
  27. Modify Term Update Redirection
  28. Check if current term is a child of another term
  29. get_terms() doesn’t return empty terms even though hide_empty is false
  30. SQL QUERY needed to get POST category (taxonomy) ? – MUST be SQL statement
  31. Archive template for taxonomy terms
  32. Custom metabox for menu administration page?
  33. Custom Fields and performance
  34. Looping Through Custom Tax Terms and Displaying All Posts For Each
  35. How to get the top most term (top ancestor) of a custom taxonomy child term?
  36. Automatically assign taxonomy term if custom meta value exists
  37. Function to limit the number of posts in taxonomy.php
  38. WP Query with custom taxonomy
  39. How to display custom taxonomy in multiple columns?
  40. Storing data into custom taxonomies VS post custom fields (post meta)
  41. Custom taxonomies making WP very slow – Way to fix?
  42. Removing the “Popular Terms” area from the Taxonomy Edit Screen in the Admin Area
  43. Sorting taxonomy columns by meta value numeric
  44. Programatically added attribute, set to ‘show on product page’ automatically. Woocommerce [closed]
  45. Reverse traversing taxonomy based on term_id
  46. Specifying a size when displaying an image associated with a taxonomy through ACF
  47. Get Current Custom Taxonomy ID by Post ID
  48. Custom fields to taxonomy
  49. I used the Tax-meta-class by bainternet but i still can’t get it to display any of the results.
  50. Autogenerate Front End Form Field With jQuery
  51. Retrieve value of a category’s custom field
  52. Styling Taxonomy Terms Individually
  53. Taxonomies on custom taxonomies
  54. How to join result of different taxonomies?
  55. How to add Post Format Taxonomy Archive page in the menu?
  56. How to get all taxonomies which can be added in menu?
  57. WordPress Tag or Custom Taxonomy Return All Posts if has that Word in Post Title
  58. Replace taxonomy permalinks
  59. Custom Taxonomy Term Archive Page Template that Filters 2 or more Taxonomies
  60. Create custom taxonomy and Display in metabox dropdown
  61. Redirect to another page using contact form 7? [closed]
  62. How to create a custom taxonomy using a shortcode?
  63. Override Taxonomy Template
  64. How Parent Taxonomy automatically added to the post when using `wp_set_object_terms()`?
  65. Get object for a few selected taxonomies
  66. Using Advanced Custom Fields Relationship Field to select a taxonomy term
  67. Dropdown taxonomy lists in admin menu
  68. Get A Custom Field From A Custom Taxonomy Of A Custom Post Type [closed]
  69. Taxonomy archive template that shows posts from more than one taxonomy
  70. How to display posttypes and taxonomy in standard posts, not in a separate label?
  71. How to get the term description in a taxonomy term archive query?
  72. How to define %category% for custom taxonomies?
  73. Create multiple taxonomies with custom fields values on the fly when creating new posts
  74. How do I get the correct URL?
  75. Connect ACF field + custom taxonomy [closed]
  76. Custom Taxonomies Archive Page 404
  77. How to replace custom post type with custom taxonmy in permalinks
  78. Display Custom Field or Custom Taxonomy in front page /post/product
  79. Cloning product not copying custom taxonomies
  80. Create new Taxonomy, add extra fields, register terms AND extra fields values?
  81. Display custom tax in “while” loop
  82. Get Highest and Lowest get_term_meta() value from Taxonomy Term
  83. How to get a terms and posts associated with another term?
  84. Displaying subcategories and then posts in taxonomy template
  85. How to use two same taxonomy in same post differently?
  86. How to Manage and link certain custom taxonomy?
  87. Display taxonomy term slugs
  88. Can I use multi (sub) levels of relation (AND | OR) on custom query?
  89. Index page of posts tagged with two separate taxonomies
  90. How to use tax_query other than by slug or id or solve custom taxonomy tags conflicts with pre-existing tags?
  91. Avoiding stripping of HTML in Custom Taxonomy Meta Field
  92. How to permanently delete a taxonomy
  93. Advanced AND tax_query in sidebar with 2 taxonomies
  94. Alternative for is_taxonomy() to workaround theme’s default sidebar
  95. What is the current page’s Taxonomy?
  96. Get custom taxonomy term url on archive page
  97. Display woocommerce product_cat child terms with thumbnails
  98. Converting Categories (with ACF fields) to custom taxonomies
  99. Adding new terms to custom taxonomy
  100. Taxonomies starting with a hyphen (minus) to assign B.C. dates to a post