PHP Conference Japan 2024

La classe UnderflowException

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

Introduction

Exception émise lorsqu'une opération invalide est effectuée sur un conteneur vide, tel qu'une suppression d'élément.

Synopsis de la classe

class UnderflowException extends RuntimeException {
/* Propriétés héritées */
protected string $message = "";
private string $string = "";
protected int $code;
protected string $file = "";
protected int $line;
private array $trace = [];
private ?Throwable $previous = null;
/* Méthodes héritées */
public Exception::__construct(string $message = "", int $code = 0, ?Throwable $previous = null)
final public Exception::getCode(): int
final public Exception::getFile(): string
final public Exception::getLine(): int
final public Exception::getTrace(): array
}
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Jakub Adamczyk
2 years ago
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 ...
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