get_metadata() WP 1.0

Retrieve metadata for the specified object.

Return

Mixed. Single metadata value, or array of values

Usage

get_metadata( $meta_type, $object_id, $meta_key, $single );

$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)

Metadata key. If not specified, retrieve all metadata for the specified object.
Default: ''

$single(true/false)

If true, return only the first value of the specified meta_key. This parameter has no effect if meta_key is not specified.
Default: false

Changelog

Code of get metadata: wp-includes/meta.php ^{WP 5.4.2}

<?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();
	}
}

Related Functions

From tag: Metadatas (any)