Idea to help solve CodeIgniter Query Builder issue with SELECT strings being exploded at commas.

DB_query_builder.php

    	/**
	 * Select
	 *
	 * Generates the SELECT portion of the query
	 *
	 * @param	string
	 * @param	mixed
	 * @return	CI_DB_query_builder
	 */
	public function select($select = '*', $escape = NULL)
	{
		if (is_string($select))
		{
			// Find all parentheses sets.
			preg_match_all('/\((.*)\)/', $select, $func_groups);

			// Inside each parentheses set, replace all commas with
			// a temporary value, which will be reverted back later.
			// We do this to avoid issues with using explode() later.
			foreach ($func_groups as $func_group)
			{
				$func_replace = str_replace(',', '{comma}', $func_group);
				$select = str_replace($func_group, $func_replace, $select);
			}

			$select = explode(',', $select);
		}

		// If the escape value was not set will will base it on the global setting
		is_bool($escape) OR $escape = $this->_protect_identifiers;

		foreach ($select as $val)
		{
			// Put commas back in where they were temporarily replaced.
			$val = str_replace('{comma}', ',', trim($val));

			if ($val !== '')
			{
				$this->qb_select[] = $val;
				$this->qb_no_escape[] = $escape;

				if ($this->qb_caching === TRUE)
				{
					$this->qb_cache_select[] = $val;
					$this->qb_cache_exists[] = 'select';
					$this->qb_cache_no_escape[] = $escape;
				}
			}
		}

		return $this;
	}

This worked great for me. Thank you.