Problem with $post_id object’s property

I consider this question to be borderline unanswerable. It really depends on context.

In your example $post is whatever that global has been set to. That is pretty general, pretty obvious, and not really saying much but without knowing the context in which this code executes it is hard to give a better answer.

That variable is set for each post in the Loop by setup_postdata or the_post and it is set on some back-end pages in similar ways, based ultimately in $_GET or $_POST data whether that $_GET or $_POST data contains a post ID or components of a query.

Many of the hooks and filters that you use are passed that value so it is not always necessary to grab the global directly.

Related Posts:

  1. Remove Custom Taxonomy Metabox from Custom Post Type Screen
  2. How do I set the default admin sort order for a custom post type to a custom column?
  3. Can you make a custom metabox field be required to save a new post?
  4. Action hook on Edit custom post type?
  5. Display content from custom meta boxes in revisions
  6. Changing the priority of a custom taxonomy’s metabox
  7. manage posts custom column is not populating data from meta boxes
  8. How to get custom metabox image field?
  9. Detect meta value changes when post is updated (post_updated)
  10. Custom field being erased after autosave
  11. How to select one major category (or custom taxonomy) for a custom post type?
  12. How can i add a metabox to pull list of custom posts (any two) on edit or add post screen?
  13. How to add a select menu to this metabox code?
  14. Cleanest way to code “Custom Write Panels/Meta Boxes”?
  15. Custom post type’s slug gets wrong when adding a custom meta box
  16. Metabox saving values
  17. Having trouble with custom post type / meta box
  18. Custom Meta Boxes – Nonce Issue – Move to trash issue
  19. How to add meta boxes(repeater fields) from WordPress back end?
  20. Displaying Meta Box Image
  21. Change Post Title Edit Box
  22. Multiple information using custom post type
  23. How to keep a check box in custom meta box for custom post type checked by default for add new post?
  24. Show metabox in custom-post-template depending on taxonomy term?
  25. How to add a “custom” date field to a custom post type?
  26. Meta Box Only in CPT Edit Page, Not in Add New
  27. get_post_meta is returning image id
  28. Why do I lose the content of meta boxes when I leave the page?
  29. WordPress nl2br is not converting newline to html line break when saving metabox value
  30. Create custom PAGE with register_post_type
  31. Populate Custom Fields in a Custom Post Type?
  32. Duplicate Custom Header Functionality into the post edit screen
  33. Send email button in custom post type backend
  34. Custom meta box data array: foreach not working correctly?
  35. What’s the difference between same wp functions get_posts(); functions in different form?
  36. how to check if custom post type column already exists?
  37. How to check if user meta field is empty in conditional else statement
  38. Custom Post Type with Templates using Meta Boxes?
  39. Post Quote with image on header for news site
  40. How to Create an Image Upload Box for Custom Posts?
  41. How to store multiple values in 1 meta_key with radio input?
  42. Extending AZIndex plugin to use custom post types and custom taxonomies
  43. A better way to add a meta box to custom post types
  44. Why are taxonomy terms not saving when using custom meta boxes with radio button taxonomy selectors?
  45. Create Connection Between two post types
  46. Disable closing on metaboxes
  47. Order a custom post type admin screen by a second custom post type title
  48. Create a Dropdown from Custom Post Type
  49. meta box on custom post type
  50. Listing custom terms in custom post meta
  51. Can’t publish custom post type – “You are not allowed to edit this post.”
  52. Moving meta boxes in admin
  53. Can I restrict category availability?
  54. Custom columns doesn’t appear in custom post type
  55. Displaying a div from an assigned meta_value when on a page
  56. How To Display A List Of CPT Posts In A Meta Box On Menus Page?
  57. populate array with posts
  58. Retrieving meta-box from a custom-post-type
  59. Create a custom post type for a photo post
  60. How to insert data into meta box from another plugin?
  61. Getting post attchment URL to populate a CPT Admin Page Column
  62. Display metaboxes if checkbox ir marked
  63. Create a select metabox that the user can pupolate?
  64. Display custom meta on page that has been check in custom post type
  65. Meta box data is saved but NOT displayed in the meta box text field. Why?
  66. Sanitaizing Select Optin For Custom Post Type Metabox in WP
  67. Saving metabox keys and storing values as array
  68. How to sum values from all custom posts metabox
  69. Custom sortable column with WPAlchemy
  70. Sortable column with custom data by date
  71. Publish box in CPT remove ‘edit’ link
  72. Saving a Custom Post Type with a Meta Box results in a “Updating Failed” error
  73. Adding accordion-section to custom post type edit screen
  74. I’m having trouble with Related Product “tax_query” ‘terms’ value
  75. WP_List_Table Inside Metabox Not Working on Clicking Search Button
  76. wp_editor in custom post type is not saving formatted text like bold, italic etc
  77. Add other all taxonomies as meta boxes to custom post type
  78. Metaboxes in Loop
  79. How save custom meta type posts multicheck grouped by taxonomy (with CMB2) [closed]
  80. Custom meta box data not saving
  81. Collect custom post in a calendar
  82. Meta Box not being added in plugin
  83. Unable to get the values for metaboxes for custom post type
  84. Custom meta-box for all custom post types
  85. Howto: use existing post_meta as options for a different metabox (checkboxes or list)
  86. Meta-Box to add multiple items one at a time and on publish save all
  87. WPAlchemy Metabox rewriting slug
  88. Displaying wp post categories into my custom metabox
  89. Filter CPT based on meta box value using Flexible Posts widget?
  90. Add Metabox to all custom post types
  91. Loading one meta box only on post-new.php with a forward link
  92. Textarea type on one field custom add_meta_box?
  93. Extending a CPT by Created by another plugin
  94. Creating entries with image attachements within posts and managing them in a list
  95. Adding a custom “Add Custom Field” button to Custom Meta boxes
  96. add a “list” into add meta box : problem
  97. Show search for data extracted from metabox
  98. Issues on saving data from CPT select metabox
  99. Remove custom meta boxes from custom post type
  100. My custom meta box with textarea field not saved