php 和Java 调用的区别?报错

demo.java
PKCS7Tool tool = PKCS7Tool.getSigner('/taobao.pfx', '1111', '1111');
String dataStr = orderNo + "|" + orderTime + "|" + curCode + "|" + orderAmount + "|" + merchantNo;
byte[] data = dataStr.getBytes("UTF-8");
String signature = tool.sign(data);
对应php
demo.php
require_once("java/Java.inc");//必须包含的配置文件
java_require("pkcs7.jar");//引用包含的jar包
$PKCS7Tool = new Java("com.bocnet.common.security.PKCS7Tool");//产生实例
$signer = $PKCS7Tool->getSigner("D://www/phpjava/taobao.pfx",'11111111','11111111');
$signature = $signer.sign("00000000000");

我的php文件下 不能这样直接调用到 sign ？？？？
报错是Fatal error: Call to undefined function sign() in D:\www\phpjava\test.php on line 14