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

Retrieves the value of a metadata field for the specified object type and ID.


Description

If the meta field exists, a single value is returned if $single is true, or an array of values if it’s false.

If the meta field does not exist, the result depends on get_metadata_default().
By default, an empty string is returned if $single is true, or an empty array if it’s false.

See also


Parameters

$meta_type

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

$object_id

(Required) ID of the object metadata is for.

$meta_key

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

Default value: ''

$single

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

Default value: false


Return

(mixed) An array of values if $single is false.<br> The value of the meta field if $single is true.<br> False for an invalid $object_id (non-numeric, zero, or negative value), or if $meta_type is not specified.<br> An empty string if a valid but non-existing object ID is passed.


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 WP-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 Object ID.
	 * @param string            $meta_key  Meta 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();
}


Changelog

Changelog
Version Description
2.9.0 Introduced.