WP_List_Table::get_column_info()

	protected function get_column_info() {
		// $_column_headers is already set / cached
		if ( isset( $this->_column_headers ) && is_array( $this->_column_headers ) ) {
			// Back-compat for list tables that have been manually setting $_column_headers for horse reasons.
			// In WP-4.3, we added a fourth argument for primary column.
			$column_headers = array( array(), array(), array(), $this->get_primary_column_name() );
			foreach ( $this->_column_headers as $key => $value ) {
				$column_headers[ $key ] = $value;
			}

			return $column_headers;
		}

		$columns = get_column_headers( $this->screen );
		$hidden = get_hidden_columns( $this->screen );

		$sortable_columns = $this->get_sortable_columns();
		/**
		 * Filters the list table sortable columns for a specific screen.
		 *
		 * The dynamic portion of the hook name, `$this->screen->id`, refers
		 * to the ID of the current screen, usually a string.
		 *
		 * @since WP-3.5.0
		 *
		 * @param array $sortable_columns An array of sortable columns.
		 */
		$_sortable = apply_filters( "manage_{$this->screen->id}_sortable_columns", $sortable_columns );

		$sortable = array();
		foreach ( $_sortable as $id => $data ) {
			if ( empty( $data ) )
				continue;

			$data = (array) $data;
			if ( !isset( $data[1] ) )
				$data[1] = false;

			$sortable[$id] = $data;
		}

		$primary = $this->get_primary_column_name();
		$this->_column_headers = array( $columns, $hidden, $sortable, $primary );

		return $this->_column_headers;
	}