Source

File: wp-includes/wp-db.php

public function get_col_info( $info_type = 'name', $col_offset = -1 ) {
		$this->load_col_info();

		if ( $this->col_info ) {
			if ( -1 === $col_offset ) {
				$i         = 0;
				$new_array = array();
				foreach ( (array) $this->col_info as $col ) {
					$new_array[ $i ] = $col->{$info_type};
					$i++;
				}
				return $new_array;
			} else {
				return $this->col_info[ $col_offset ]->{$info_type};
			}
		}
	}