wpdb::set_prefix( string $prefix, bool $set_table_names = true ): string|WP_Error

1005	public function set_prefix( $prefix, $set_table_names = true ) {1006 1007		if ( preg_match( '|[^a-z0-9_]|i', $prefix ) ) {1008			return new WP_Error( 'invalid_db_prefix', 'Invalid database prefix' );1009		}1010 1011		$old_prefix = is_multisite() ? '' : $prefix;1012 1013		if ( isset( $this->base_prefix ) ) {1014			$old_prefix = $this->base_prefix;1015		}1016 1017		$this->base_prefix = $prefix;1018 1019		if ( $set_table_names ) {1020			foreach ( $this->tables( 'global' ) as $table => $prefixed_table ) {1021				$this->$table = $prefixed_table;1022			}1023 1024			if ( is_multisite() && empty( $this->blogid ) ) {1025				return $old_prefix;1026			}1027 1028			$this->prefix = $this->get_blog_prefix();1029 1030			foreach ( $this->tables( 'blog' ) as $table => $prefixed_table ) {1031				$this->$table = $prefixed_table;1032			}1033 1034			foreach ( $this->tables( 'old' ) as $table => $prefixed_table ) {1035				$this->$table = $prefixed_table;1036			}1037		}1038		return $old_prefix;1039	}