The second I pressed submit on the post above I realized my issue.
Because we can add multiple participants. I need to go one deeper in the array.
$pData = array();
$pData = array('firstname'=>"testFirst", 'lastname'=>'testLasy',"email"=>"firstname.lastname@example.org");
// and now I can add multiple.
$addParticipant = $myJSONRPCClient-add_participants($sessionKey,$survey_id,$pData );
Thanks for the help.
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