php - >在级联中使用的运算符

I saw this code:

 public function query( $query )
    {
        $full_query = $this->link->query( $query );
        if( $this->link->error )
        {
            $this->log_db_errors( $this->link->error, $query );
            return false; 
        }
        else
        {
            return true;
        }
    }

included in a class definition. Please explain what this kind of code means: a->b->c. I know that a->b is used When accessing a method or a property of an instantiated class. But can not understand how to interpret("read,understand,translate") a->b->c

It means that property b of object a is also an object. So you're getting property c of property b of object a.

class a {
    public $b;

    function __construct() {
        $this->b = new b;
    }
}

class b {
    public $c;

    function __construct() {
        $this->c = 'Hello';
    }
}

$a = new a;

echo $a->b->c; // outputs Hello.

Object a has a property, b, that is itself an object having c as a method or property. In terms of the code posted, $this, the object whose source you are viewing has a property -link - that is an object. Since link is also an object, it can (and does) have properties, two of which are query and error.