Trying to write a apex class for making Salesforce and PayPal work via Form Assembly. I've created a custom object called Donation and am using a template coding provided by From Assembly support (http://www3.formassembly.com/blog/doc/connectors/salesforce/advanced-integration/making-salesforce-and-paypal-work-together/). I changed the code to replace where it referenced Opportunity to reference my custom object Donation__c. But I get the error ' Error: Compile Error: Variable does not exist: donation__c at line 8 column 9'. Below is the cod I'm using. Any Ideas?

public class IPNHandlerController {

    public PageReference myIPNupdate() {
     try{
        PageReference pageRef = ApexPages.currentPage();
        //Get the value of the 'custom' parameter from current page
        String paramCustom = pageRef.getParameters().get('custom');
        donation__c = [select Id,paid__c from Donation__c where FormAssemblyID__c = :paramCustom ];

        String content = '';
        for(String key : pageRef.getParameters().keySet()){
            //Note that there is no guarantee of order in the parameter key map.
            content += key + ' : ' + pageRef.getParameters().get(key) + '\n';
        }
        Donation__c.PayPalInfo__c = content;
        Donation__c.paid__c = True;
        update Donation__c;

        PageReference newPage = new ApexPages.StandardController(Donation__c).view();
        newPage.setRedirect(true);       

        return newPage;
     } catch (System.Exception e){
         //A failure occurred
         system.debug(e);
         return null;
     }
    }

    public Opportunity opportunity {get; set;}

    public IPNHandlerController() {
    }
}