Possible parsing bug for quotes.

I seem to be getting a bug on the following statement.

<a href='#' onclick='displayPrices("<?php echo "volumeDiscount".$i?>");return false;' >

I get <unterminated statement>.

If I write the same statement as:

<a href='#' onclick='displayPrices("volumeDiscount<?php echo $i?>");return false;' >

it works correctly.