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There is a custom field array that then contains each custom field within it as a sub-object. This is the same way that lists work on contact objects. See below:
$contact -> custom_fields = [ [ "name" => "CustomField1" , "Value" => $_POST [ 'CustomField1' ] ], [ "name"=>"CustomField2", "Value"=>$_POST['CustomField2'] ] ] ;
Regards, David B. Tier II API Support Engineer
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