<?php
include('phpseclib1.0.16/Crypt/RSA.php');
include('/phpseclib1.0.16/Math/BigInteger.php');

 $client = Yii::$app->soapApi;

      $sha256Pass = hash("sha256", Yii::$app->params['passCode']); //perform SHA-256 of the password

      $result = new \Math_BigInteger($sha256Pass, 16); //in base-16
      $exponent= Yii::$app->params['exponent']; //this value will be replaced with what was documented
      $modulus= Yii::$app->params['modulus']; //this value will be replaced with what was documented

      $crypt_rsa = new \Crypt_RSA();
      $crypt_rsa->loadKey(
         array(
             'e' => new \Math_BigInteger($exponent),
             'n' => new \Math_BigInteger($modulus)
         )
      );

      $encryptedPassword = base64_encode($crypt_rsa->encrypt($result));

      $parameters = [
        'username' =>'usertest1a',
        'password' => $encryptedPassword,
        'orgid' => '1184'
      ];

      var_dump($client->createTokenString($parameters));
    }