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 ...
The UnderflowException class
(PHP 5 >= 5.1.0, PHP 7)
Introducere
Exception thrown when performing an invalid operation on an empty container, such as removing an element.
Sinopsisul clasei
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User Contributed Notes 2 notes
Jakub Adamczyk ¶
1 year ago
evguenia dot chagnon at gmail dot com ¶
7 years ago
UnderflowException handles exceptions due to a value being too small to maintain precision, resulting in loss of accuracy. In PHP, this can occurs when using floats:
echo (1-0.9) // 0.1
echo (1-0.99) // 0.01
echo (1-0.999) // 0.001
echo (1-0.9999) // 9.9999999999989E-05
echo (1-0.99999) // 9.9999999999545E-06
echo (1-0.999999) // 1.0000000000288E-06
