delete_metadata( string $meta_type, int $object_id, string $meta_key, mixed $meta_value = '', bool $delete_all = false )

function delete_metadata( $meta_type, $object_id, $meta_key, $meta_value = '', $delete_all = false ) {
    global $wpdb;

    if ( ! $meta_type || ! $meta_key || ! is_numeric( $object_id ) && ! $delete_all ) {
        return false;
    }

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

    $table = _get_meta_table( $meta_type );
    if ( ! $table ) {
        return false;
    }

    $type_column = sanitize_key( $meta_type . '_id' );
    $id_column   = ( 'user' === $meta_type ) ? 'umeta_id' : 'meta_id';

    // expected_slashed ($meta_key)
    $meta_key   = wp_unslash( $meta_key );
    $meta_value = wp_unslash( $meta_value );

    /**
     * Short-circuits deleting 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:
     *
     *  - `delete_post_metadata`
     *  - `delete_comment_metadata`
     *  - `delete_term_metadata`
     *  - `delete_user_metadata`
     *
     * @since 3.1.0
     *
     * @param null|bool $delete     Whether to allow metadata deletion of 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      $delete_all Whether to delete the matching metadata entries
     *                              for all objects, ignoring the specified $object_id.
     *                              Default false.
     */
    $check = apply_filters( "delete_{$meta_type}_metadata", null, $object_id, $meta_key, $meta_value, $delete_all );
    if ( null !== $check ) {
        return (bool) $check;
    }

    $_meta_value = $meta_value;
    $meta_value  = maybe_serialize( $meta_value );

    $query = $wpdb->prepare( "SELECT $id_column FROM $table WHERE meta_key = %s", $meta_key );

    if ( ! $delete_all ) {
        $query .= $wpdb->prepare( " AND $type_column = %d", $object_id );
    }

    if ( '' !== $meta_value && null !== $meta_value && false !== $meta_value ) {
        $query .= $wpdb->prepare( ' AND meta_value = %s', $meta_value );
    }

    $meta_ids = $wpdb->get_col( $query );
    if ( ! count( $meta_ids ) ) {
        return false;
    }

    if ( $delete_all ) {
        if ( '' !== $meta_value && null !== $meta_value && false !== $meta_value ) {
            $object_ids = $wpdb->get_col( $wpdb->prepare( "SELECT $type_column FROM $table WHERE meta_key = %s AND meta_value = %s", $meta_key, $meta_value ) );
        } else {
            $object_ids = $wpdb->get_col( $wpdb->prepare( "SELECT $type_column FROM $table WHERE meta_key = %s", $meta_key ) );
        }
    }

    /**
     * Fires immediately before deleting 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).
     *
     * Possible hook names include:
     *
     *  - `delete_post_meta`
     *  - `delete_comment_meta`
     *  - `delete_term_meta`
     *  - `delete_user_meta`
     *
     * @since 3.1.0
     *
     * @param string[] $meta_ids    An array of metadata entry IDs to delete.
     * @param int      $object_id   ID of the object metadata is for.
     * @param string   $meta_key    Metadata key.
     * @param mixed    $_meta_value Metadata value.
     */
    do_action( "delete_{$meta_type}_meta", $meta_ids, $object_id, $meta_key, $_meta_value );

    // Old-style action.
    if ( 'post' === $meta_type ) {
        /**
         * Fires immediately before deleting metadata for a post.
         *
         * @since 2.9.0
         *
         * @param string[] $meta_ids An array of metadata entry IDs to delete.
         */
        do_action( 'delete_postmeta', $meta_ids );
    }

    $query = "DELETE FROM $table WHERE $id_column IN( " . implode( ',', $meta_ids ) . ' )';

    $count = $wpdb->query( $query );

    if ( ! $count ) {
        return false;
    }

    if ( $delete_all ) {
        $data = (array) $object_ids;
    } else {
        $data = array( $object_id );
    }
    wp_cache_delete_multiple( $data, $meta_type . '_meta' );

    /**
     * Fires immediately after deleting 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).
     *
     * Possible hook names include:
     *
     *  - `deleted_post_meta`
     *  - `deleted_comment_meta`
     *  - `deleted_term_meta`
     *  - `deleted_user_meta`
     *
     * @since 2.9.0
     *
     * @param string[] $meta_ids    An array of metadata entry IDs to delete.
     * @param int      $object_id   ID of the object metadata is for.
     * @param string   $meta_key    Metadata key.
     * @param mixed    $_meta_value Metadata value.
     */
    do_action( "deleted_{$meta_type}_meta", $meta_ids, $object_id, $meta_key, $_meta_value );

    // Old-style action.
    if ( 'post' === $meta_type ) {
        /**
         * Fires immediately after deleting metadata for a post.
         *
         * @since 2.9.0
         *
         * @param string[] $meta_ids An array of metadata entry IDs to delete.
         */
        do_action( 'deleted_postmeta', $meta_ids );
    }

    return true;
}