Description:
------------
Column name is not double quoted

% psql -U testuser testdb
testdb=# CREATE TABLE t_test ("c1" char(10), "C2" char(10));
testdb=# \q

% ./test.php
INSERT INTO t_test (c1,C2) VALUES ('0','0');

% psql -U testuser testdb
testdb=# INSERT INTO t_test (c1,C2) VALUES ('0','0');
ERROR:  column "c2" of relation "t_test" does not exist

Reproduce code:
---------------
(test.php)
#!/usr/local/bin/php
<?php
$db = pg_connect('dbname=testdb user=testuser');
$vals['c1'] = '0';
$vals['C2'] = '0';
echo pg_insert($db, 't_test', $vals, PGSQL_DML_STRING);
?>

Expected result:
----------------
INSERT INTO t_test (c1,"C2") VALUES ('0','0');

Actual result:
--------------
INSERT INTO t_test (c1,C2) VALUES ('0','0');