This one has me pulling my hair out. I noticed that advanced search was returning negative results when it shouldn't, so I turned on error reporting and got the following warning:
Warning: Cannot modify header information - headers already sent by (output started at /home/username/public_html/includes/languages/english/theme198/advanced_search_result.php:19) in /home/username/public_html/includes/functions/functions_general.php on line 44
I checked advanced_search_result.php and there were are no spaces or extra lines before or after the opening or closing PHP tags. There are no single quotes within a single-quoted string that I could find, and the double quotes are appropriately within single quotes. I temporarily took everything extra out of the file. Here's what it looks like:
Code:
<?php
define('NAVBAR_TITLE_1', 'Advanced Search');
define('NAVBAR_TITLE_2', 'Search Results');
define('HEADING_TITLE', 'Advanced Search');
define('HEADING_SEARCH_CRITERIA', 'Search Criteria');
define('TEXT_SEARCH_IN_DESCRIPTION', 'Search In Product Descriptions');
define('ENTRY_CATEGORIES', 'Categories:');
define('ENTRY_INCLUDE_SUBCATEGORIES', 'Include Subcategories');
define('ENTRY_MANUFACTURERS', 'Manufacturers:');
define('ENTRY_PRICE_FROM', 'Price From:');
define('ENTRY_PRICE_TO', 'Price To:');
define('ENTRY_DATE_FROM', 'Date From:');
define('ENTRY_DATE_TO', 'Date To:');
define('TEXT_SEARCH_HELP_LINK', 'Search Help [?]');
define('TEXT_ALL_CATEGORIES', 'All Categories');
define('TEXT_ALL_MANUFACTURERS', 'All Manufacturers');
define('HEADING_SEARCH_HELP', 'Search Help');
define('TEXT_SEARCH_HELP', 'Keywords may be separated by AND and/or OR statements for greater control of the search results.<br /><br />For example, Microsoft AND mouse would generate a result set that contain both words. However, for mouse OR keyboard, the result set returned would contain both or either words.<br /><br />Exact matches can be searched for by enclosing keywords in double-quotes.<br /><br />For example, "notebook computer" would generate a result set which match the exact string.<br /><br />Brackets can be used for further control on the result set.<br /><br />For example, Microsoft and (keyboard or mouse or "visual basic").');
define('TEXT_CLOSE_WINDOW', 'Close Window [x]');
define('TABLE_HEADING_IMAGE', 'Product Image');
define('TABLE_HEADING_MODEL', 'Model');
define('TABLE_HEADING_PRODUCTS', 'Product Name');
define('TABLE_HEADING_MANUFACTURER', 'Manufacturer');
define('TABLE_HEADING_QUANTITY', 'Quantity');
define('TABLE_HEADING_PRICE', 'Price');
define('TABLE_HEADING_WEIGHT', 'Weight');
define('TABLE_HEADING_BUY_NOW', 'Buy Now');
define('TEXT_NO_PRODUCTS', 'There is no product that matches the search criteria.');
define('ERROR_AT_LEAST_ONE_INPUT', 'At least one of the fields in the search form must be entered.');
define('ERROR_INVALID_FROM_DATE', 'Invalid From Date.');
define('ERROR_INVALID_TO_DATE', 'Invalid To Date.');
define('ERROR_TO_DATE_LESS_THAN_FROM_DATE', 'To Date must be greater than or equal to From Date.');
define('ERROR_PRICE_FROM_MUST_BE_NUM', 'Price From must be a number.');
define('ERROR_PRICE_TO_MUST_BE_NUM', 'Price To must be a number.');
define('ERROR_PRICE_TO_LESS_THAN_PRICE_FROM', 'Price To must be greater than or equal to Price From.');
define('ERROR_INVALID_KEYWORDS', 'Invalid keywords.');
?>
I tried substituting the advanced_search_result.php file from the default template, but it generates the same error (on a different line, of course).

I have eliminated all the usual culprits for this error, I think, and haven't found any other posts regarding this file, so I must be missing something. I also ran through the FAQ on header already sent errors with no luck.

Can anyone see what I'm missing?

I'm using Zen 1.3.8 with the recent security patch. There are no extensions for search functions installed.

TIA