I'm newbie and I would like to enrich my working lead-creator API with using assigment rules.

I found that I should precede the creating code with

$useDefaultRule = new soapval('useDefaultRule', null, 'true');

$crmHandle->setHeader('AssignmentRuleHeader', array($useDefaultRule));

but it gives that setHeader() is an undefined method.

how could I fix the problem?

thanks for the answers