isset 再 php7 中出现的问题

isset-post-user.php

<?php

class Model
{
    // 存放属性
    protected $attributes = [];

    // 存放关系
    protected $relations = [];

    function __get($key)
    {
        if( isset($this->attributes[$key]) ) {
            return $this->attributes[$key];
        }

        if (method_exists($this, $key)) {
            return $this->getRelationshipFromMethod($key);
        }
    }

    protected function getRelationshipFromMethod($method)
    {
        $relation = $this->$method();

        return $this->relations[$method] = $relation;
    }

    public function __set($k, $v)
    {
        $this->attributes[$k] = $v;
    }

    public function __isset($key)
    {
        if (isset($this->attributes[$key]) || isset($this->relations[$key])) {
            return true;
        }

        // 关键是这个处理  5.1.35 中没有, 注释这句就可以看到效果
        if (method_exists($this, $key) && $this->$key && isset($this->relations[$key]     )) {
            return true;
        }

        return false;
    }
}

class Post extends Model
{

    protected function user()
    {
        $user = new User();
        $user->name = 'user name';
        return $user;
    }


}

class User extends Model
{
}


$post = new Post();
echo '对象未赋值：';
echo isset($post->content) ? 'true' : 'false';
echo PHP_EOL;

$post->content = 'foobar';
echo '对象赋值：';
echo isset($post->content) ? 'true' : 'false';
echo PHP_EOL;

echo 'isset post 的 user 的名字：';
echo isset($post->user->name) ? 'true' : 'false';
echo PHP_EOL;

// 先赋值
echo 'post 的 user 的名字：';
echo $post->user->name;
echo PHP_EOL;

echo 'isset post 的 user 的名字：';
echo isset($post->user->name) ? 'true' : 'false';
echo PHP_EOL;