Solve the problem that the isset method is always false after upgrading to php7

A problem occurred after the company upgraded php7, similar to this isset($post->user->name) is always false, the previous php 5.6 was normal , the laravel version is 5.1.35 (it has not been upgraded for a long time).

Let’s take a look firstisset

##isset is used to detect whether the variable is set

First let’s do Look at an official example

which roughly means the following

<?php

class Post
{
    protected $attributes = [&#39;content&#39; => &#39;foobar&#39;];

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

$post = new Post();
echo isset($post->content);  // false

The above example will always return

false, because foo is not Post attribute, but __get taken out

Magic method __isset

So how to solve it What about the question above? Using magic methods

<?PHP
class Post
{
    protected $attributes = [&#39;content&#39; => &#39;foobar&#39;];

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

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

        return false;
    }
}

$post = new Post();
echo isset($post->content);   //true

Examples similar to

Eloquent

Looking at the code of laravel 5.1.35, we write a simple example ourselves

First A

Model, simple implementation. __get, __set, __isset

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

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

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

          // 找到关联的对象，放在关系里面
        if (method_exists($this, $key)) {

              $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;
        }

        return false;
    }
}

Then we define a

Post Moel and a User Moel

class Post extends Model
{

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

}

class User extends Model
{
}

Okay, let’s verify it

isset

$post = new Post();

echo 'isset 发帖用户：';
echo isset($post->user) ? 'true' : 'false';  // false
echo PHP_EOL;

echo 'isset 发帖用户的名字：';
echo isset($post->user->name) ? 'true' : 'false';  // false
echo PHP_EOL;

echo '发帖用户的名字：';
echo $post->user->name;    // user name
echo PHP_EOL;

echo '再次判断 isset 发帖用户的名字：';
echo isset($post->user->name) ? 'true' : 'false';   // true
echo PHP_EOL;

Answer

Analyzing the above results, it feels like php 7

The isset method has changed its judgment on the object. If it is executed once first, $post->user->name, that is, user is placed in post's relations , such that isset($post->user) is true, and then isset($post->user- >name) is true.

Finally found the answer in the

git log of Eloquent model,

PHP 7 has fixed a bug with __isset which affects both the 
native isset and empty methods. This causes specific issues 
with checking isset or empty on relations in Eloquent. In 
PHP 7 checking if a property exists on an unloaded relation, 
for example isset($this->relation->id) is always 
returning false because unlike PHP 5.6, PHP 7 is now 
checking the offset of each attribute before chaining to 
the next one. In PHP 5.6 it would eager load the relation 
without checking the offset. This change brings back the 
intended behavior of the core Eloquent model __isset method 
for PHP 7 so it works like it did in PHP 5.6.

For reference, please check the following link, 
specifically Nikita Popov's comment (core PHP dev) - 
https://bugs.php.net/bug.php?id=69659

is roughly when php7 isset judges, it will judge in sequence. php5.6 will preload relationships. In fact, laravel has already done related processing, so after upgrading laravel, this problem will naturally disappear.

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