The UnderflowException class
(PHP 5 >= 5.1.0)
Introduction
Exception thrown when performing an invalid operation on an empty container, such as removing an element.
Class synopsis
- PHP Руководство
- Функции по категориям
- Индекс функций
- Справочник функций
- Другие базовые расширения
- Стандартная библиотека PHP (SPL)
- Класс BadFunctionCallException
- Класс BadMethodCallException
- Класс DomainException
- The InvalidArgumentException class
- Класс LengthException
- Класс LogicException
- Класс OutOfBoundsException
- Класс OutOfRangeException
- Класс OverflowException
- Класс RangeException
- Класс RuntimeException
- Класс UnderflowException
- Класс UnexpectedValueException
Коментарии
The most typical usage is with stack, queue or collection, for example when you queue tasks, make call stack or manipulate JSON, XML, etc. elements.
As other exepctions of RuntimeException class, this type of error can't be detected in (for example) your IDE or compiler.
<?php
// Functions declared above
$f1 = function() { setTypeControl('username');};
$f2 = function() { setTypeControl('userpass');};
$f3 = function() { setButton('Add');};
$f4 = function() { setButton('OK');};
$tasks = new class {
private $list;
// Create internal queue
public function __construct() {
$this->list = new SplQueue;
}
// Add to queue
public function add(callable $func) {
$this->list->enqueue($func);
}
// Delete from queue and execute
public function do() {
if ($this->list->isEmpty()) {
throw new UnderflowException;
} else {
call_user_func($this->list->dequeue());
}
}
};
$tasks->add($f1);
$tasks->add($f2);
$tasks->add($f3);
$tasks->add($f4);
$tasks->do(); // Field username is created
$tasks->do(); // Field userpass is created
$tasks->do(); // Button Add is created
$tasks->do(); // Button OK is created
$tasks->do(); // Fatal error: Uncaught UnderflowException in ...