php5 Introduction to the object assignment mechanism of PHP5

Copy code The code is as follows:

class SimpleClass{
public $var = 'a default value';
public function displayVar() {
echo $this->var;
}
}
$instance = new SimpleClass();
$assigned = $instance;
$reference =& $instance;
$instance->var = '$assigned will have this value';
$instance = null; / / $instance and $reference become null var_dump($instance);var_dump($reference);var_dump($assigned);
var_dump($instance);
var_dump($assigned);
var_dump($reference);
?> ;

php5 rewrites the OOP bottom layer. When a class generates an instance (object), the return value $instance is not the object itself, but just an id (or resource handle) of the object. Therefore, when $instance is assigned to $assigned, $assigned also points to This object is a bit like the reference (&) operation of an ordinary variable. Therefore, when $instance is initialized, $assigned is also initialized. However, when $instance is destroyed (=null), because the corresponding object still has a handle ($assigned), the object will not be destroyed and the destructor will not be triggered. As a result, var_dump($assigned) is the value of the object, and $instance is already an empty handle, showing null. Because $reference has a reference relationship similar to that of ordinary variables with $instance, it also becomes an empty handle and displays null.

The above has introduced the object assignment mechanism of php5 PHP5, including the content of php5. I hope it will be helpful to friends who are interested in PHP tutorials.