I have an online lead generation business and a subscription to Salesforce.com Enterprise Edition. 

I want to find someone who's experienced with Salesforce's API and can help me create some tight, simple PHP code to insert and update Person Accounts in Salesforce.com from the forms on my websites. 

These are pretty simple HTML form, think 10-20 fields max. The architecture is as follows: 
- each Person Account will be uniquely ID'd by a combo of IP address and name, or, if no name is given (which is a possibility), just IP address 
- when a form is submitted, the script needs to: 

1) search Salesforce to see if that combo of IP and name already exists as a Person Account 
2) if it does, then create a closed Opportunity for that Person Account which contains info on the form submitted (the university degree program the person is interested in, the $$ value of that lead, the time/date submitted, etc.) 
3) if it does not, then create the Person Account record first (with IP, source info, name and address etc. from the form), and then create the Opportunity per #2 above 

I use a handful of the out-of-the-box fields for Person Account objects, and a bunch of custom ones.  The code will need some rudimentary error handling etc. as well.

This should be very easy money for someone who knows PHP and the Force.com API.  I have to believe there are people out there who have created this exact kind of setup before.

I know a little bit of PHP and a very little bit about the API, and this is an important enough piece of code that I would rather just pay someone and make sure it's done right. 

Please respond with details of your experience with both PHP and the Force.com API. 

Thanks! 
Joe