Parse SELECT clause of SQL queries into a PHP array

This is more for analysing a query in PHP before it's sent to the server. Very complicated why I'm doing this, so I'd rather not go into the reason for this.

In PHP, I need to store the field selections into a PHP array. So take this query for example:

SELECT user_id,username,DATE(join_datetime) as join_date, (SELECT COUNT(1) FROM foobar WHERE foonum IN (5,4,6) and user_id = users.user_id) as myfoo_count 
FROM users 
WHERE user_id = 123

In this case I need to store user_id,username,DATE(join_datetime) as join_date, (SELECT COUNT(1) FROM foobar WHERE foonum IN (5,4,6) and user_id = users.user_id) as myfoo_count into an array exploded by a comma (,). So I would get:

array (
  [1] => 'user_id',
  [2] => 'username',
  [3] => 'DATE(join_datetime) as join_date',
  [4] => '(SELECT COUNT(1) FROM foobar WHERE foonum IN (5,4,6) and user_id = users.user_id) as myfoo_count'
)

I have gotten as far as extracting the fields part of the query, but I'm stuck on trying to explode the fields by comma. The main problem being with subqueries which might have commas in them too (see example).

For anyone coming across this question in the future someone has already gone to the trouble of writting an SQL parser in PHP.

At present it supports SELECT, INSERT, UPDATE, DELETE and REPLACE statements.

You would have to write a parser almost as complex as MySQL's query parser (written in YACC/Bison for C). It's not going to be a regular expression or a little string manipulation. This is a nonregular language, you can't parse them without an actual parser.

You can't just walk through the string finding commas and parentheses either, SQL is much more complex than that. You have expressions within expressions, function calls, conditional logic, etc. all of which can be nested arbitrarily deep with commas and parentheses all over.

http://dev.mysql.com/doc/refman/5.0/en/expressions.html

If you really want to do this with PHP, you have a big job ahead of yourself.