如何解决js里面的php代码报错问题

<span style="color:rgb(0,0,0);
   font-family:Consolas, Inconsolata, Courier, monospace;font-size:12px;
   background-color:rgb(255,255,255);">Undefined variable：loginUserName
</span>

<script>
    Ext.onReady(function () {
        var app = Ext.create("PSI.App", {
         //   userName: "{$loginUserName}",
            productionName: "{$productionName}"
        });
       
    });
</script>

    /**
     * 业务日志 - 主页面
     */
    public function index()
    {
        $us = new UserService();

        if ($us->hasPermission(FIdConst::USE_ORDER)) {
            $this->initVar();

           // $this->assign("loginUserName", "tom");
 

            $this->display();
        } else {
            $this->gotoLoginPage("/Home/");
        }
    }

//   userName: "{$loginUserName}",

//   userName: "<?php echo ( $loginUserName); ?>",

 // $this->assign("loginUserName", "tom");

 //   userName: "{$loginUserName}",