get_metadata( string $meta_type, int $object_id, string $meta_key = '', bool $single = false )

Retrieves metadata for the specified object.

Contents

Parameters Parameters

$meta_type

(string) (Required) Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user', or any other object type with an associated meta table.

$object_id

(int) (Required) ID of the object metadata is for.

$meta_key

(string) (Optional) Metadata key. If not specified, retrieve all metadata for the specified object.

Default value: ''

$single

(bool) (Optional) If true, return only the first value of the specified meta_key. This parameter has no effect if meta_key is not specified.

Default value: false

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Return Return

(mixed) Single metadata value, or array of values

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Uses Uses

Uses
Uses Description
wp-includes/cache.php: wp_cache_get()

Retrieves the cache contents from the cache by key and group.
wp-includes/functions.php: absint()

Convert a value to non-negative integer.
wp-includes/functions.php: maybe_unserialize()

Unserialize value only if it was serialized.
wp-includes/plugin.php: apply_filters()

Calls the callback functions that have been added to a filter hook.
wp-includes/meta.php: update_meta_cache()

Updates the metadata cache for the specified objects.
wp-includes/meta.php: get_{$meta_type}_metadata

Filters whether to retrieve metadata of a specific type.
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Used By Used By

Used By
Used By Description
wp-includes/ms-site.php: get_site_meta()

Retrieves metadata for a site.
wp-includes/rest-api/fields/class-wp-rest-meta-fields.php: WP_REST_Meta_Fields::update_multi_meta_value()

Updates multiple meta values for an object.
wp-includes/rest-api/fields/class-wp-rest-meta-fields.php: WP_REST_Meta_Fields::update_meta_value()

Updates a meta value for an object.
wp-includes/rest-api/fields/class-wp-rest-meta-fields.php: WP_REST_Meta_Fields::update_value()

Updates meta values.
wp-includes/rest-api/fields/class-wp-rest-meta-fields.php: WP_REST_Meta_Fields::get_value()

Retrieves the meta field value.
wp-includes/meta.php: get_registered_metadata()

Retrieves registered metadata for a specified object.
wp-includes/taxonomy.php: get_term_meta()

Retrieves metadata for a term.
wp-includes/user.php: get_user_meta()

Retrieve user meta field for a user.
wp-includes/post.php: get_post_meta()

Retrieves a post meta field for the given post ID.
wp-includes/comment.php: get_comment_meta()

Retrieve comment meta field for a comment.
wp-includes/meta.php: update_metadata()

Updates metadata for the specified object. If no value already exists for the specified object ID and metadata key, the metadata will be added.
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Source Source

File: wp-includes/meta.php 

function get_metadata( $meta_type, $object_id, $meta_key = '', $single = false ) {
	if ( ! $meta_type || ! is_numeric( $object_id ) ) {
		return false;
	}

	$object_id = absint( $object_id );
	if ( ! $object_id ) {
		return false;
	}

	/**
	 * Filters whether to retrieve metadata of a specific type.
	 *
	 * The dynamic portion of the hook, `$meta_type`, refers to the meta
	 * object type (comment, post, term, or user). Returning a non-null value
	 * will effectively short-circuit the function.
	 *
	 * @since 3.1.0
	 *
	 * @param null|array|string $value     The value get_metadata() should return - a single metadata value,
	 *                                     or an array of values.
	 * @param int               $object_id ID of the object metadata is for.
	 * @param string            $meta_key  Metadata key.
	 * @param bool              $single    Whether to return only the first value of the specified $meta_key.
	 */
	$check = apply_filters( "get_{$meta_type}_metadata", null, $object_id, $meta_key, $single );
	if ( null !== $check ) {
		if ( $single && is_array( $check ) ) {
			return $check[0];
		} else {
			return $check;
		}
	}

	$meta_cache = wp_cache_get( $object_id, $meta_type . '_meta' );

	if ( ! $meta_cache ) {
		$meta_cache = update_meta_cache( $meta_type, array( $object_id ) );
		if ( isset( $meta_cache[ $object_id ] ) ) {
			$meta_cache = $meta_cache[ $object_id ];
		} else {
			$meta_cache = null;
		}
	}

	if ( ! $meta_key ) {
		return $meta_cache;
	}

	if ( isset( $meta_cache[ $meta_key ] ) ) {
		if ( $single ) {
			return maybe_unserialize( $meta_cache[ $meta_key ][0] );
		} else {
			return array_map( 'maybe_unserialize', $meta_cache[ $meta_key ] );
		}
	}

	if ( $single ) {
		return '';
	} else {
		return array();
	}
}

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Changelog Changelog

Changelog
Version Description
2.9.0 Introduced.

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User Contributed Notes User Contributed Notes

  2. Skip to note 2 content
    You must log in to vote on the helpfulness of this noteVote results for this note: 0You must log in to vote on the helpfulness of this note
    Contributed by Sylvain Schellenberger —

    Example of returned array for post metadatas :

    array (
  '_pingme' => array (
    0 => '1',
  ),
  '_encloseme' => array (
    0 => '1',
  ),
  'custom key 1' => array (
    0 => 'custom value 1',
    1 => 'custom value 2',
  ),
  'custom key 2' => array (
    0 => 'custom value 3',
  ),
)

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