API / XML question

API / XML question

I'm writing a php script in Wordpress to insert a record into Zoho using the API.  I've got a functional script working, and I'm able to create records as long as I strip almost all special characters.

If I try to insert a $ sign or %, for example, Zoho will not create a record.  

To include a shortened snippet:

  1. $interestRate = "5.5%";
  2. $xmlData = "<Leads>
  3.       <row no='1'>
  4.       <FL val='First Name'>John</FL>
  5.       <FL val='Interest Rate'>" . $interestRate . "</FL>
  6.       </row>
  7.       </Leads>";

If I remove the % manually, or by using preg_replace, I can get the record to insert.
I've also tried doing:
  1. <FL val='Interest Rate'><![CDATA[" . $interestRate . "]]></FL>

Am I not taking the right steps?