add_metadata() WordPress Function

The add_metadata() function is used to add metadata to a post. It takes two parameters: the post ID and the metadata key. The value of the metadata key will be the value of the metadata.

add_metadata( string $meta_type, int $object_id, string $meta_key, mixed $meta_value, bool $unique = false ) #

Adds metadata for the specified object.

Contents

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)(Required)Metadata key.

$meta_value

(mixed)(Required)Metadata value. Must be serializable if non-scalar.

$unique

(bool)(Optional) Whether the specified metadata key should be unique for the object. If true, and the object already has a value for the specified metadata key, no change will be made.

Default value: false

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Return

(int|false) The meta ID on success, false on failure.

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Source

File: wp-includes/meta.php

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function add_metadata( $meta_type, $object_id, $meta_key, $meta_value, $unique = false ) {
    global $wpdb;
 
    if ( ! $meta_type || ! $meta_key || ! is_numeric( $object_id ) ) {
        return false;
    }
 
    $object_id = absint( $object_id );
    if ( ! $object_id ) {
        return false;
    }
 
    $table = _get_meta_table( $meta_type );
    if ( ! $table ) {
        return false;
    }
 
    $meta_subtype = get_object_subtype( $meta_type, $object_id );
 
    $column = sanitize_key( $meta_type . '_id' );
 
    // expected_slashed ($meta_key)
    $meta_key   = wp_unslash( $meta_key );
    $meta_value = wp_unslash( $meta_value );
    $meta_value = sanitize_meta( $meta_key, $meta_value, $meta_type, $meta_subtype );
 
    /**
     * Short-circuits adding metadata of a specific type.
     *
     * The dynamic portion of the hook name, `$meta_type`, refers to the meta object type
     * (post, comment, term, user, or any other type with an associated meta table).
     * Returning a non-null value will effectively short-circuit the function.
     *
     * Possible hook names include:
     *
     *  - `add_post_metadata`
     *  - `add_comment_metadata`
     *  - `add_term_metadata`
     *  - `add_user_metadata`
     *
     * @since 3.1.0
     *
     * @param null|bool $check      Whether to allow adding metadata for the given type.
     * @param int       $object_id  ID of the object metadata is for.
     * @param string    $meta_key   Metadata key.
     * @param mixed     $meta_value Metadata value. Must be serializable if non-scalar.
     * @param bool      $unique     Whether the specified meta key should be unique for the object.
     */
    $check = apply_filters( "add_{$meta_type}_metadata", null, $object_id, $meta_key, $meta_value, $unique );
    if ( null !== $check ) {
        return $check;
    }
 
    if ( $unique && $wpdb->get_var(
        $wpdb->prepare(
            "SELECT COUNT(*) FROM $table WHERE meta_key = %s AND $column = %d",
            $meta_key,
            $object_id
        )
    ) ) {
        return false;
    }
 
    $_meta_value = $meta_value;
    $meta_value  = maybe_serialize( $meta_value );
 
    /**
     * Fires immediately before meta of a specific type is added.
     *
     * The dynamic portion of the hook name, `$meta_type`, refers to the meta object type
     * (post, comment, term, user, or any other type with an associated meta table).
     *
     * Possible hook names include:
     *
     *  - `add_post_meta`
     *  - `add_comment_meta`
     *  - `add_term_meta`
     *  - `add_user_meta`
     *
     * @since 3.1.0
     *
     * @param int    $object_id   ID of the object metadata is for.
     * @param string $meta_key    Metadata key.
     * @param mixed  $_meta_value Metadata value.
     */
    do_action( "add_{$meta_type}_meta", $object_id, $meta_key, $_meta_value );
 
    $result = $wpdb->insert(
        $table,
        array(
            $column      => $object_id,
            'meta_key'   => $meta_key,
            'meta_value' => $meta_value,
        )
    );
 
    if ( ! $result ) {
        return false;
    }
 
    $mid = (int) $wpdb->insert_id;
 
    wp_cache_delete( $object_id, $meta_type . '_meta' );
 
    /**
     * Fires immediately after meta of a specific type is added.
     *
     * The dynamic portion of the hook name, `$meta_type`, refers to the meta object type
     * (post, comment, term, user, or any other type with an associated meta table).
     *
     * Possible hook names include:
     *
     *  - `added_post_meta`
     *  - `added_comment_meta`
     *  - `added_term_meta`
     *  - `added_user_meta`
     *
     * @since 2.9.0
     *
     * @param int    $mid         The meta ID after successful update.
     * @param int    $object_id   ID of the object metadata is for.
     * @param string $meta_key    Metadata key.
     * @param mixed  $_meta_value Metadata value.
     */
    do_action( "added_{$meta_type}_meta", $mid, $object_id, $meta_key, $_meta_value );
 
    return $mid;
}

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Uses

Uses
UsesDescription
wp-includes/meta.php:get_object_subtype()

Returns the object subtype for a given object ID of a specific type.

wp-includes/cache.php:wp_cache_delete()

Removes the cache contents matching key and group.

wp-includes/formatting.php:wp_unslash()

Removes slashes from a string or recursively removes slashes from strings within an array.

wp-includes/formatting.php:sanitize_key()

Sanitizes a string key.

wp-includes/functions.php:absint()

Convert a value to non-negative integer.

wp-includes/functions.php:maybe_serialize()

Serialize data, if needed.

wp-includes/plugin.php:apply_filters()

Calls the callback functions that have been added to a filter hook.

wp-includes/plugin.php:do_action()

Calls the callback functions that have been added to an action hook.

wp-includes/wp-db.php:wpdb::get_var()

Retrieves one variable from the database.

wp-includes/wp-db.php:wpdb::insert()

Inserts a row into the table.

wp-includes/wp-db.php:wpdb::prepare()

Prepares a SQL query for safe execution.

wp-includes/meta.php:_get_meta_table()

Retrieves the name of the metadata table for the specified object type.

wp-includes/meta.php:sanitize_meta()

Sanitizes meta value.

wp-includes/meta.php:add_{$meta_type}_metadata

Short-circuits adding metadata of a specific type.

wp-includes/meta.php:add_{$meta_type}_meta

Fires immediately before meta of a specific type is added.

wp-includes/meta.php:added_{$meta_type}_meta

Fires immediately after meta of a specific type is added.

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Used By

Used By
Used ByDescription
wp-includes/ms-site.php:add_site_meta()

Adds metadata to 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/taxonomy.php:add_term_meta()

Adds metadata to a term.

wp-includes/user.php:add_user_meta()

Adds meta data to a user.

wp-includes/post.php:add_post_meta()

Adds a meta field to the given post.

wp-includes/comment.php:add_comment_meta()

Adds meta data field to 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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Changelog

Changelog
VersionDescription
2.9.0Introduced.
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