get_post_meta($post->ID) returns empty string when in preview mode of custom post type

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I've got my custom post type 'event'. I got tne next code in single-event.php:

get_header();
the_post();
echo '<pre>';
echo "$post->ID\n";
var_dump(get_post_meta($post->ID));
echo '</pre>';

When I open my event page by normal URI /event/slug/, I got this:

22681
array(17) {
  ["_edit_lock"]=>
  array(1) {
    [0]=>
    string(13) "1439329938:36"
  }
  ["_edit_last"]=>
  array(1) {
    [0]=>
    string(2) "36"
  }
...
}

When I open it for preview, like /event/slug/?preview=true&preview_id=22681&preview_nonce=XXXXXXXXXXXXX , I got only this:

22681
string(0) ""

(where first line is a correct post ID and is the same as preview_id param)

What am I doing wrong? And why string(0), and not array(0)?

I've got my custom post type 'event'. I got tne next code in single-event.php:

get_header();
the_post();
echo '<pre>';
echo "$post->ID\n";
var_dump(get_post_meta($post->ID));
echo '</pre>';

When I open my event page by normal URI /event/slug/, I got this:

22681
array(17) {
  ["_edit_lock"]=>
  array(1) {
    [0]=>
    string(13) "1439329938:36"
  }
  ["_edit_last"]=>
  array(1) {
    [0]=>
    string(2) "36"
  }
...
}

When I open it for preview, like /event/slug/?preview=true&preview_id=22681&preview_nonce=XXXXXXXXXXXXX , I got only this:

22681
string(0) ""

(where first line is a correct post ID and is the same as preview_id param)

What am I doing wrong? And why string(0), and not array(0)?

• post-meta
• previews

Share Improve this question asked Aug 11, 2015 at 22:04 SergeAxSergeAx 12711 silver badge88 bronze badges 2

• codex.wordpress.org/Function_Reference/… – Mayeenul Islam Commented Aug 12, 2015 at 7:01
• Hi, @mayeenul-islam! Thank you for your reply, but it is not what I meant. What I have is get_post_meta returns essentially nothing - no underscored fields and no regular fields when called from preview. – SergeAx Commented Aug 22, 2015 at 13:06

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2 Answers 2

Sorted by: Reset to default 0

I solved this problem with 3 lines of code after calling get_post_meta():

if (!is_array($post_meta)) { 
    $post_meta = array();
}

The answer to your question why it returns an empty string is listed in the comment of the get_post_meta() entry in the WP Developers docs: https://developer.wordpress.org/reference/functions/get_post_meta/#comment-825

The function requires the following: get_post_meta( $postID, 'meta_key', $single=false );

As the comment of the link above explains: If a meta field with the given $key isn’t found for the given $post_id, the return value varies:

If $single is true, an empty string is returned. If $single is false, an empty array is returned.

$single defaults to false and no meta_key has been given, therefore an empty array is returned.

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