How do you update post date (year only) in a separate custom field?

I would like to update all my posts with a custom field that stores the year the post was published.

The "year" value will obviously be retrieved from the post's date meta data.

I will then use the value stored to query posts with a certain plugin.

So far, I have this, but not sure where this code should go and if it needs modification!

$year_published = get_the_date( 'Y' ); 
update_post_meta(get_the_ID(), 'year_date', '$year_published' );

I would like to update all my posts with a custom field that stores the year the post was published.

The "year" value will obviously be retrieved from the post's date meta data.

I will then use the value stored to query posts with a certain plugin.

So far, I have this, but not sure where this code should go and if it needs modification!

$year_published = get_the_date( 'Y' ); 
update_post_meta(get_the_ID(), 'year_date', '$year_published' );

• posts
• custom-field
• date
• date-time
• post-meta

Share Improve this question edited Dec 3, 2018 at 15:22 Qjoey asked Dec 3, 2018 at 12:28 QjoeyQjoey 111 bronze badge 4

• There are a few approaches to this, but firstly, you will need to fix your code with: update_post_meta( get_the_ID(), 'year_date', $year_published ); – Christine Cooper ♦ Commented Dec 3, 2018 at 12:54
• Thanks Christine. could you suggest one short approach? I would like to update all existing and future posts. Preferably without using a plugin? – Qjoey Commented Dec 3, 2018 at 12:58
• 1 I suggest hooking into save post and storing the custom meta data. And also looping through all existing posts and updating the value... – Christine Cooper ♦ Commented Dec 3, 2018 at 14:12
• So I managed to loop through and update the values... However, when I inspect post meta fields, both the month and year are only storing empty strings ' ' instead of the actual value. Please see my answer below and help point out any edits to fix this. – Qjoey Commented Dec 3, 2018 at 21:38

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1 Answer 1

Sorted by: Reset to default 0

So I was first looking for a way to loop through the existing posts, as suggested in Christine's comment. Based on this answer, I created a basic plugin that runs the loop upon activation.

// Run the loop when the plugin is activated
register_activation_hook(__FILE__, 'update_my_metadata');
function update_my_metadata(){
$args = array(
    'post_type' => 'post', // Only get the posts
    'post_status' => 'publish', // Only the posts that are published
    'posts_per_page'   => -1 // Get every post
);
$posts = get_posts($args);
foreach ( $posts as $post ) {
    // Run a loop and update every meta data
    $month=get_the_date('M');
    $year=get_the_date('Y');
    update_post_meta($post->ID, 'month-field', $month); echo $month;
    update_post_meta($post->ID, 'year-field', $year); echo $year;
 }
}

However, when I inspect post meta fields, both the month and year are only storing empty strings '' instead of the actual date value.

Any suggestions?