The Data source "salesforce_source.php" has been updated to support ALL wsdl methods  using Query function.

<?php
class Opportunityt extends AppModel {
	var $useDbConfig='sftest';
	var $useTable = false;
	function OpportunityIdByAccountNumber($account_number = null) {
		$SOQL = "SELECT
					Id
					FROM  Opportunity 
				WHERE  Account_Number__c = '".$account_number."'";
		return $this->query(array('query',$SOQL));
	}
}
?>

 Note the  $this->query(array('methodname', data1, data2, data 3);


Here is a call using the Upsert method from a controller:

<snip>
                       $sObjects                = array();

                       for (...) {
                                 $sObject                  = new stdClass();
                                 $sObject->Id           = '12345678OOOABC';
                                 $sObject->Amount  = '10001.00';
                                 array_push($sObjects, $sObject);
                       }
              $success = $this->Opportunityt->query(array('upsert', $sObjects, 'Opportunity'));		
			
			if ($success->success == 1) {
			print_r("<br><b>UPSERT SUCCESS</b><br>");
			} else {
			print_r( "<br><font color=\"#FF0000\"><b>UPSERT ERROR</b></font><br><pre>");
					print_r($success->errors);
					echo "</pre>";
			}
</snip>

The above uses a modified version of the SforceEnterpriseClient.php that changes upsert method to be more PHP rational.

mod to upsert follows:

/**
   * Creates new objects and updates existing objects; uses a custom field to
   * determine the presence of existing objects. In most cases, we recommend
   * that you use upsert instead of create because upsert is idempotent.
   * Available in the API version 7.0 and later.
   *
   * @param array  $sObjects    Array of sObjects
   * @param string $objectType  Name of Sf object to upsert to
   * @param string $ext_Id      Field the id matching is set to ID by default
   * @return UpsertResult       stdClass Object
   */
  public function upsert($sObjects, $objectType = "Contact", $ext_Id ='ID' ) {
    $arg = new stdClass;
    $arg->externalIDFieldName = new SoapVar($ext_Id, XSD_STRING, 'string', 'http://www.w3.org/2001/XMLSchema');
    foreach ($sObjects as &$sObject) {
      $sObject = new SoapVar($sObject, SOAP_ENC_OBJECT, $objectType, $this->namespace);
    }
    $arg->sObjects = $sObjects;
    return parent::_upsert($arg);
  }

 Here is the new salesforce_source.php

<?php
require_once ('models/datasources/soapclient/SforceEnterpriseClient.php');
/**
* SalesForceSource
* 
* A Slaesforce SOAP Client Datasource
* Connects to a Salesforce enterprise SOAP server using the configured wsdl file
*
* PHP Version 5
* Copyright 2009 Chris Roberts Ph.D, www.osxgnu.org
* This library is free software: you can redistribute it and/or modify
* it. 
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 
*/
class SalesforceSource extends DataSource {

/**
* Description for this DataSource
*
* @var string
*/
	public $description = 'Salesforce Enterprise SOAP Client DataSource';

/**
* The SoapClient instance
*
* @var object
*/
	public $client = null;

/**
* The current connection status
*
* @var boolean
*/
	public $connected = false;
	
/**
* The default configuration
*
* @var array
*/
	public $_baseConfig = array(
	'wsdl' => '',
	'username' => '',
	'password' => ''
	);

/**
* Constructor
*
* @param array $config An array defining the configuration settings
*/
	public function __construct($config) {
		parent::__construct($config);
		$this->connect();
	}

	public function isConnected(){
		return true;
	}

/**
* Connects to the SOAP server using the wsdl in the configuration
* passes the salesforce credentals for login
* @param array $config An array defining the new configuration settings
* @return boolean True on success, false on failure
*/
	public function connect() {
		if (empty($this->config['username']) || empty($this->config['password']) || empty($this->config['wsdl'])) {
			$this->error = "Your username-password-wsdl must all be set";
		    $this->showError();
			return false;
		}
		$wsdl = APP.'models/datasources/soapclient/'.$this->config['wsdl'];
		$mySforceConnection = new SforceEnterpriseClient();
		$mySforceConnection->createConnection($wsdl);
		$mySoapClient = $mySforceConnection->createConnection($wsdl);
		$mylogin = $mySforceConnection->login($this->config['username'], $this->config['password']);
		$this->client = $mySforceConnection;

		return $mySforceConnection;
	}

/**
* Sets the SoapClient instance to null
*
* @return boolean True
*/
	public function close() {
		$this->client = null;
		$this->connected = false;
		return true;
	}

/**
* Returns the available SOAP methods
*
* @return array List of SOAP methods
*/
	public function listSources() {
		$this->client = $this->connect();
		return $this->client->__getFunctions();
	}

/**
* Query the SOAP server with the given method and parameters
* pass the SOQL query as the only pram
* @return mixed Returns the soql object array result on success, false on failure
*/
public function query() {
 $this->error = false;
        $this->client = $this->connect();
        $args = array();
        $arg = func_get_args();
        $args = $arg[0];
        $method = null;
        $queryData = null;
 		$type =null;
        if(count($args) >1) {
            $method = $args[0];
            $queryData = $args[1];
        } else {
        	$queryData = $args[0];
        }        
        try {
	        	if(count($args) > 1){
	        		if (isset($args[2])   ){
        					$result = $this->client->$method($queryData, $args[2]);
        			} else {
	        			$result = $this->client->$method($queryData);
        			}
	        	} else {
	        		$result = $this->query($arg);
	        	}
        } catch (SoapFault $fault) {
            $this->error = $fault->faultstring;
        }
        
        if($this->error) {
            $this->showError();
            return false;
        } else {
            return $result;
        }
    }
    

/**
* Returns the last SOAP response
*
* @return string The last SOAP response
*/
	public function getResponse() {
		return $this->client->__getLastResponse();
	}

	/**
* Returns the last SOAP request
*
* @return string The last SOAP request
*/
	public function getRequest() {
		return $this->client->__getLastRequest();
	}

/**
* Shows an error message and outputs the SOAP result if passed
*
* @param string $result A SOAP result
* @return string The last SOAP response
*/
	public function showError($result = null) {
		if(Configure::read() > 0) {
			if($this->error) {
				trigger_error('<span style = "color:Red;text-align:left"><b>SalesForce Error:</b> <pre>' . print_r($this->error) . '</pre></span>', E_USER_WARNING);
			}
			if($result) {
				e(sprintf("<p><b>Result:</b> %s </p>", $result));
			}
		}
	}

}

?>