PHP interceptor unset usage

PHP Interceptor (Interceptor) is a PHP extension mechanism that can intercept and modify PHP runtime behavior through the interceptor. Common interceptors include __construct(), __destruct(), __get(), etc. This article will introduce the usage of unset(), a commonly used interceptor in PHP.

unset() is an important function in PHP, used to delete variables, but in some scenarios, we cannot delete variables directly, such as the properties of objects. At this time, you need to use the unset() interceptor to implement the function of deleting object attributes.

In PHP, if you want to delete object attributes, you can use the unset() function, for example:

class Person {
  public $name = 'Tom';

  public function __unset($property) {
    echo "Deleting property '" . $property . "'\n";
    unset($this->$property);
  }
}

$person = new Person();
unset($person->name);

In the above code, we created a Person class and defined a name attribute . In the class, we use the __unset() method to intercept the deletion of the attribute, and output the deleted attribute name in this method, and finally use the unset() function to delete the attribute.

Although there is only one attribute in this example, in actual development, we often need to delete multiple attributes. At this time, we can use the switch statement in the __unset() method to determine the attribute name to be deleted, for example ：

class Person {
  public $name = 'Tom';
  public $age = 20;

  public function __unset($property) {
    switch ($property) {
      case 'name':
        echo "Deleting property 'name'\n";
        unset($this->name);
        break;
      case 'age':
        echo "Deleting property 'age'\n";
        unset($this->age);
        break;
      default:
        echo "Property '" . $property . "' not found\n";
        break;
    }
  }
}

$person = new Person();
unset($person->name);
unset($person->age);
unset($person->address);

In the above code, we added a new $age attribute and added a switch statement in the __unset() method to delete multiple attributes. If the attribute name to be deleted does not exist, the corresponding prompt message will be output.

It should be noted that if the __unset() method is used in the class, be sure to use the unset() function when deleting attributes, otherwise PHP will report an error.

In addition to deleting object attributes, the unset() interceptor can also be used to delete global variables. Example:

function test() {
  global $name;
  $name = 'Tom';
}

function __unset($name) {
  echo "Deleting global variable '" . $name . "'\n";
  unset($GLOBALS[$name]);
}

test();
unset($name);

In the above code, we define a test() method, use the global keyword to define the $name variable as a global variable, and assign it the value 'Tom'. In the __unset() method, we use the echo statement to output the name of the global variable to be deleted, and use the unset() function to delete the variable. Finally, we call the unset() function to delete the $name variable, and the __unset() method will be executed.

Summary

PHP interceptor is a very practical mechanism that can intercept and modify PHP behavior at runtime. This article introduces the usage of unset(), a common interceptor in PHP interceptors, which can be used to delete object properties and global variables. When using the unset() interceptor, be sure to use the unset() function to delete variables, otherwise PHP will report an error.

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