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<?php $etag = '"123-456\"789"'; $regex = '~(?:^|[\h,]+)(?:W/)?(")?(?(1)((?:[^"\\\\]|\\\\.)*(*MARK:Q))(?:"|\\\\|$)|([^,]*(*MARK:T)))~'; \preg_match_all($regex, $etag, $matches, \PREG_SET_ORDER); print_r($matches); var_dump(strpos('123\'123', '\\'));

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