Description:
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When running a basic query through the filter_var function using FILTER_SANITIZE_STRING and FILER_FLAG_NO_ENCODE_QUOTES a portion of my string is being stripped out that shouldn't be.

Test script:
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$sql = "SELECT customer, kdaccount, expDateMonth, expDateYear, nameid FROM creditcard_main WHERE ((expDateYear = '2016' AND expDateMonth <= '01') OR (expDateYear >= '2015' AND expDateMonth >= '07')) AND cardStatus = '1' AND cardAuthorized = '1' ORDER BY kdaccount ASC LIMIT 0, 25";

$query = filter_var ($sql, FILTER_SANITIZE_STRING,
    FILTER_FLAG_NO_ENCODE_QUOTES);die;

Expected result:
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Should be identical to original string:

$query = "SELECT customer, kdaccount, expDateMonth, expDateYear, nameid FROM creditcard_main WHERE ((expDateYear = '2016' AND expDateMonth <= '01') OR (expDateYear >= '2015' AND expDateMonth >= '07')) AND cardStatus = '1' AND cardAuthorized = '1' ORDER BY kdaccount ASC LIMIT 0, 25"

Actual result:
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$query = "SELECT customer, kdaccount, expDateMonth, expDateYear, nameid FROM creditcard_main WHERE ((expDateYear = '2016' AND expDateMonth = '2015' AND expDateMonth >= '07')) AND cardStatus = '1' AND cardAuthorized = '1' ORDER BY kdaccount ASC LIMIT 0, 25"