QuickBooks/IPP/OAuth.php
public function signature($method, $keyfile = null)
	{
		$this->_signature = $method;
		$this->_keyfile = $keyfile;
	}
public function signature($method, $keyfile = null)
	{
		$this->_signature = $method;
		$this->_keyfile = $keyfile;
	}
Set the signature method