count
A simple copy function that not only copies the given array but ensures the copy's pointer is set to the exact same position:
function array_copy(&array)
{
$key = key($array);
$copy = $array;
while (($copy_key = key($copy)) !== NULL) {
if ($copy_key == $key) break;
next($copy);
}
return $copy;
}
That's all ... bye.
current
(PHP 4, PHP 5)
current — Zwraca bieżący element tablicy
Opis
Każda tablica ma wewnętrzny wskaźnik bo swojego "bieżącego" elementu, który jest inicjalizowany do pierwszego elementu wstawionego do tablicy.
Funkcja current() po prostu zwraca wartość elementu tablicy, na który aktualnie wskazuje wewnętrzny wskaźnik. Nie przesuwa ona wskaźnika. Jeśli wewnętrzny wskaźnik jest poza końcem listy elementów, current() zwraca FALSE.
Ostrzeżenie
Ta funkcja może zwrócić logiczne FALSE, ale także zwykłą wartość rozpoznawaną jako FALSE, na przykład 0 lub "". Więcej informacji w rozdziale dotyczącym typów logicznych. Użyj operatora === aby sprawdzić wartość i typ zwracany przez tę funkcję.
Informacja: Nie będziesz mógł odróznić końca tablicy od elementu FALSE typu bool'owskiego. Aby poprawnie przejść przez tablicę, która może zawierać elementy FALSE, zobacz funkcję each().
Przykład #1 Przykład użycia funkcji current() i innych podobnych
<?php
$transport = array('stopy', 'rower', 'samochód', 'samolot');
$tryb = current($transport); // $tryb = 'stopy';
$tryb = next($transport); // $tryb = 'rower';
$tryb = current($transport); // $tryb = 'rower';
$tryb = prev($transport); // $tryb = 'stopy';
$tryb = end($transport); // $tryb = 'samolot';
$tryb = current($transport); // $tryb = 'samolot';
?>
Patrz także: end(), key(), next(), prev() i reset() i each().
add a note
User Contributed Notescurrent
aefxx
15-May-2008 03:39
15-May-2008 03:39
gregory at gregory dot net
28-Feb-2008 05:07
28-Feb-2008 05:07
It took me a while to figure this out, but there is a more consistent way to figure out whether you really went past the end of the array, than using each().
You see, each() gets the value BEFORE advancing the pointer, and next() gets the value AFTER advancing the pointer. When you are implementing the Iterator interface, therefore, it's a real pain in the behind to use each().
And thus, I give you the solution:
To see if you've blown past the end of the array, use key($array) and see if it returns NULL. If it does, you're past the end of the array -- keys can't be null in arrays.
Nifty, huh? Here's how I implemented the Iterator interface in one of my classes:
<?php
/**
* DbRow file
* @package PalDb
*/
/**
* This class lets you use Db rows and object-relational mapping functionality.
*/
class DbRow implements Iterator
{
/**
* The DbResult object that gave us this row through fetchDbRows
* @var DbResult
*/
protected $result;
/**
* The fields of the row
* @var $fields
*/
protected $fields;
/**
* Constructor
*
* @param PDOStatement $stmt
* The PDO statement object that this result uses
* @param DbResult $result
* The result that produced this row through fetchDbRows
*/
function __construct($result)
{
$this->result = $result;
}
/**
* Get the DbResult object that gave us this row through fetchDbRows
* @return DbResult
*
* @return unknown
*/
function getResult()
{
return $this->result;
}
function __set(
$name,
$value)
{
$this->fields[$name] = $value;
}
function __get(
$name)
{
if (isset($this->fields[$name]))
return $this->fields[$name];
else
return null;
}
/**
* Iterator implementation - rewind
*/
function rewind()
{
$this->beyondLastField = false;
return reset($this->fields);
}
function valid()
{
return !$this->beyondLastField;
}
function current()
{
return current($this->fields);
}
function key()
{
return key($this->fields);
}
function next()
{
$next = next($this->fields);
$key = key($this->fields);
if (isset($key)) {
return $next[1];
} else {
$this->beyondLastField = true;
return false; // doesn't matter what we return here, see valid()
}
}
private $beyondLastField = false;
};
Hope this helps someone.
vaclav dot sir at gmail dot com
13-Aug-2007 04:23
13-Aug-2007 04:23
To that "note": You won't be able to distinguish the end of an array from a boolean FALSE element, BUT you can distinguish the end from a NULL value of the key() function.
Example:
<?php
if (key($array) === null) {
echo "You are in the end of the array.";
} else {
echo "Current element: " . current($array);
}
?>
marnaq
18-Aug-2006 12:20
18-Aug-2006 12:20
To make this function return a reference to the element instead, use:
<?php
function ¤t_by_ref(&$arr) {
return $arr[key($arr)];
}
?>
mdeng at kabenresearch dot com
24-Apr-2004 06:04
24-Apr-2004 06:04
For large array(my sample was 80000+ elements), if you want to traverse the array in sequence, using array index $a[$i] could be very inefficient(very slow). I had to switch to use current($a).
vitalib at 012 dot net dot il
02-Dec-2003 10:10
02-Dec-2003 10:10
Note that by copying an array its internal pointer is lost:
<?php
$myarray = array(0=>'a', 1=>'b', 2=>'c');
next($myarray);
print_r(current($myarray));
echo '<br>';
$a = $myarray;
print_r(current($a));
?>
Would output 'b' and then 'a' since the internal pointer wasn't copied. You can cope with that problem using references instead, like that:
<?php
$a =& $myarray;
?>
tipman
08-May-2003 11:07
08-May-2003 11:07
if you got a array with number as index you get the last index with this:
eg:
$array[0] = "foo";
$array[1] = "foo2";
$lastKey = sizeof($array) - 1;
only a little help :)
retestro_REMOVE at SPAM_esperanto dot org dot il
02-Mar-2003 02:31
02-Mar-2003 02:31
The docs do not specify this, but adding to the array using the brackets syntax:
$my_array[] = $new_value;
will not advance the internal pointer of the array. therefore, you cannot use current() to get the last value added or key() to get the key of the most recently added element.
You should do an end($my_array) to advance the internal pointer to the end ( as stated in one of the notes on end() ), then
$last_key = key($my_array); // will return the key
$last_value = current($my_array); // will return the value
If you have no need in the key, $last_value = end($my_array) will also do the job.
- Sergey.