$src = "rates/" . $src;
$dst = "rates/new_" . $src;
$srcFp = fopen($src, "r");
$dstFp = fopen($dst, "w");

/* This works above doesn't */
$srcFp = fopen("new/test.csv", "r");
$dstFp = fopen("new/new_test.csv", "w");