Question

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

Retrieve metadata for the specified object.

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description

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参数

$meta_type

(string) (Required) Type of object metadata is for (e.g., comment, post, or user)

$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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返回值

(mixed) Single metadata value, or array of values

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源代码

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, 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 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 ) );
		$meta_cache = $meta_cache[$object_id];
	}

	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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更新日志

Version	description
2.9.0	Introduced.

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相关函数

Uses

• wp-includes/cache.php: wp_cache_get()
• wp-includes/functions.php: absint()
• wp-includes/functions.php: maybe_unserialize()
• wp-includes/plugin.php: apply_filters()
• wp-includes/meta.php: update_meta_cache()
• wp-includes/meta.php: get_{$meta_type}_metadata
Show 1 more use Hide more uses

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Used By

• wp-includes/rest-api/fields/class-wp-rest-meta-fields.php: WP_REST_Meta_Fields::update_multi_meta_value()
• wp-includes/rest-api/fields/class-wp-rest-meta-fields.php: WP_REST_Meta_Fields::update_meta_value()
• wp-includes/rest-api/fields/class-wp-rest-meta-fields.php: WP_REST_Meta_Fields::get_value()
• wp-includes/meta.php: get_registered_metadata()
• wp-includes/taxonomy.php: get_term_meta()
• wp-includes/user.php: get_user_meta()
• wp-includes/post.php: get_post_meta()
• wp-includes/comment.php: get_comment_meta()
• wp-includes/meta.php: update_metadata()
Show 4 more used by Hide more used by

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User Contributed Notes