使用 trait 时报PHP Parse error: syntax error, unexpect

// Trait.php

trait CustomerFunctionsTrait {

public function plus ( $a = 1, $b = 1 ) {
echo $a + $b;
}

public function minus ( $a = 5, $b = 1 ) {
echo $a - $b;
}

}

// Test.php
include ‘./Trait.php‘;
class MyTest {
use CustomerFunctionsTrait;
public function plus () {
// use CustomerFunctionsTrait;  //这是我错的地方, 把use 写到方法体里了 - -!!
echo ‘str‘;
}
}

$n = new MyTest;
$n->minus();