You need to escape the double quote as: \"
instead of ""
$result=mysql_query("select * from jos_users INTO OUTFILE 'users.csv' FIELDS ESCAPED BY '\"' TERMINATED BY ',' ENCLOSED BY '\"' LINES TERMINATED BY '\n' ");
An un-escaped "
will prematurely terminate the string.
Example:
This is incorrect: "A " is a double quote"
This is correct: "A \" is a double quote"