isset in PHP7

The isset is not right after upgrading php7

The company has a problem after upgrading php7

Similar to this isset($post->user-> name) is always false

It was normal for PHP 5.6 before

The laravel version is 5.1.35 (it hasn’t been upgraded for a long time)

Look at isset# first

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

First let’s look at an official example

It 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 The example will always return false, because foo is not a property of Post, but a property taken out by __get

Magic method__isset

So how to solve the above problem? ? 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 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 the PHP 7 isset method's judgment of the object has changed. If it is executed once, $post->user->name, that is, user is placed in the relations of the post. , so that isset ($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

Roughly when judging by php7 isset, it will be judged in sequence. php5.6 will preload relationships. In fact, laravel also did related processing as early as May, so after upgrading laravel, this problem will naturally disappear.

Recommended tutorials: "

PHP7 Tutorial" "PHP Tutorial" "Laravel Tutorial"

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