When you’re creating a WordPress plugin or customizing your theme, you may need to store some meta information about your posts in the database. In this article, we’re going to take a look at how to use update_post_meta function to achieve exactly that.
The update_post_meta Function Definition And Arguments
<?php
function update_post_meta(int $post_id, string $meta_key, mixed $meta_value, mixed $prev_value = '')
As you can see, the function takes 4 arguments:
- $post_id – ID of the post associated with the meta data
- $meta_key – name of the meta field
- $meta_value – meta value that is to be stored
- $prev_value – optional previous value to check before updating. If specified, only update existing metadata entries with this value. Otherwise, update all entries.
How To Use The update_post_meta Function
Let’s say we want to store how many times our post has been viewed every time someone visits a post page. Here is how we can do it.
<?php
add_action('template_redirect', function() {
// Check if we're on the post page
if (! is_singular('post')) {
return;
}
global $post;
// Check how many views the post already has
$views = get_post_meta($post->ID, 'views', true);
// If no views yet are stored in the database, set the value to 0
if (empty($views)) {
$views = 0;
}
update_post_meta($post->ID, 'views', $views + 1);
});
As you can see, we first check if the page that is displayed is a post page. Then, we check how many views the post already has.
If it doesn’t have any yet, we set the value of the $views variable to 0. And then, we simply store the updated number of views using the update_post_meta function.
Functions Similar To update_post_meta Function
- get_post_meta(int $post_id, string $key = ”, bool $single = false) – the get_post_meta function retrieves a meta value for a given post.
- add_post_meta(int $post_id, string $meta_key, mixed $meta_value, bool $unique = false) – adds a custom post meta to the database
- delete_post_meta(int $post_id, string $meta_key, mixed $meta_value = ”) – deletes a post meta value from the database.
Wrapping Up
As you can see, the update_post_meta function can be handy in some situations especially when you’re building a custom theme or plugin.
