array_rand
This code will reduce array deeply.
<?php
function print_s($s) {
return is_null($s) ? "NULL" : (is_array($s) ? "Array" : ($s ? "TRUE" : "FALSE"));
}
function r_and_dp($a, $b) {
echo "phase1:" . print_s($a) . "," . print_s($b) . "<br>\n";
if(is_array($a)) {
$a = array_reduce($a, "r_and_dp");
}
if(is_array($b)) {
$b = array_reduce($b, "r_and_dp");
}
echo "phase2:" . print_s($a) . "," . print_s($b) . "<br>\n";
$a = is_null($a) ? TRUE : $a;
$b = is_null($b) ? TRUE : $b;
echo "phase3:" . print_s($a) . "," . print_s($b) . "<br>\n";
return $a && $b;
}
$bools = array(TRUE, array(FALSE, TRUE), TRUE);
echo print_s(array_reduce($bools, "r_and_dp")) . "<br>\n";
// result: FALSE
?>
When using boolean, you have to carefully set an "initial" argument.
<?php
function r_or_dp($a, $b) {
if(is_array($a)) {
$a = array_reduce($a, "r_or_dp");
}
if(is_array($b)) {
$b = array_reduce($b, "r_or_dp");
}
return (is_null($a) ? FALSE : $a) || (is_null($b) ? FALSE : $b);
}
?>
array_reduce
(PHP 4 >= 4.0.5, PHP 5)
array_reduce — Iterative Reduktion eines Arrays zu einem Wert mittels einer Callbackfunktion
Beschreibung
array_reduce() wendet die Funktion
function iterativ auf die Elemente des Arrays
input so an, dass das Array auf einen einzigen
Wert reduziert wird.
Parameter-Liste
-
input -
Das Eingabe-Array.
-
function -
Die Callbackfunktion.
-
initial -
Ist der optionale Parameter
intialangegeben, wird er am Anfang des Prozesses benutzt oder als Resultat verwendet, sollte das Array leer sein.
Rückgabewerte
Gibt den sich ergebenden Wert zurück.
Falls das Array leer ist und initial nicht
angegeben wurde, so wird array_reduce() NULL
zurückgeben.
Changelog
| Version | Beschreibung |
|---|---|
| 5.3.0 |
Der von initial akzeptierte Datentyp wurde zu
Mixed geändert, vorher war dies Integer.
|
Beispiele
Beispiel #1 array_reduce()-Beispiel
<?php
function rsum($v, $w)
{
$v += $w;
return $v;
}
function rmul($v, $w)
{
$v *= $w;
return $v;
}
$a = array(1, 2, 3, 4, 5);
$x = array();
$b = array_reduce($a, "rsum");
$c = array_reduce($a, "rmul", 10);
$d = array_reduce($x, "rsum", "Keine Daten für die Reduktion");
?>
Dies wird dazu führen, dass $b den Wert 15 beinhaltet, $c den Wert 1200 (= 10*1*2*3*4*5) und $d den Text Keine Daten für die Reduktion enthält.
Siehe auch
- array_filter() - Filtert Elemente eines Arrays mittels einer Callback-Funktion
- array_map() - Wendet eine Callback-Funktion auf die Elemente von Arrays an
- array_unique() - Entfernt doppelte Werte aus einem Array
- array_count_values() - Zählt die Werte eines Arrays
add a note
User Contributed Notesarray_reduce
yuki [dot] kodama [at] gmail [dot] com
31-Jan-2007 05:56
31-Jan-2007 05:56
bdechka at yahoo dot ca
10-Jan-2007 09:57
10-Jan-2007 09:57
The above code works better this way.
<?php
function reduceToTable($html, $p) {
$html .= "<TR><TD><a href=\"$p.html\">$p</a></td></tr>\n";
return $html;
}
$list = Array("page1", "page2", "page3");
$tab = array_reduce($list, "reduceToTable");
echo "<table>".$tab . "</table>\n";
?>
marcel dot oehler at kubusmedia dot com
08-Feb-2006 04:26
08-Feb-2006 04:26
I've just experienced some really strange behaviour of array_reduce in PHP 5.0.4:
$result = array( 0, 17, 0, 0, 33, 0, 0, 0, 0, 50);
$total = array_reduce( $result, "sumCalc", 0);
function sumCalc( $a, $b){
return $a + $b;
}
and $total equals to 83!
I know, this could be done easier, but it should work nevertheless. Has anybody experienced something similar? I will avoid using array_reduce in the future...
Seanj.jcink.com
05-Jan-2006 03:23
05-Jan-2006 03:23
The code posted below by bishop to count the characters of an array is simply... erm... well useless to me...
$array=Array("abc","de","f");
strlen(implode("",$array)); //6
works; and is much smaller. Probably much faster too.
ildar [DASH] sh [AT] mail [DOT] ru
30-Nov-2005 07:02
30-Nov-2005 07:02
in rare cases when an array is a set of numeric values and result is one of sum or product of numbers the next examples may be useful
<?php
// sum of array items
echo eval('return ' . implode('+', $nums) . ';');
// product of array items
echo eval('return ' . implode('*', $nums) . ';');
?>
the reason of these codes is omitting of single used per script of callbacks
david dot tulloh at infaze dot com dot au
23-Jun-2005 10:18
23-Jun-2005 10:18
The code supplied by cuntbubble is unfortunately incorrect.
Running it I got the output:
0<TR><TD><a href="page1.html">page1</a></td>
<TR><TD><a href="page2.html">page2</a></td>
<TR><TD><a href="page3.html">page3</a></td>
</table>
So php, not finding an integer, used int(0) to start the process. I've tested to confirm this.
bishop
01-May-2004 05:19
01-May-2004 05:19
Count the total number of characters in an array of strings:
<?php
$lines = array ('abc', 'd', 'ef');
$totalChars = array_reduce($lines, create_function('$v,$w','return $v + strlen($w);'), 0);
// $totalChars === 6
?>
tonicpeddler at aol dot com
02-Nov-2002 04:17
02-Nov-2002 04:17
in response to php dot net at cuntbubble dot com
actually when you pass a value to a function that accepts a specific data type, php automatically evaluates that value as the data type expected
php dot net at cuntbubble dot com
18-Jan-2002 05:08
18-Jan-2002 05:08
There is an error/misleading item in the documentation
[, int initial]
int is not constrained to an integer, it can be any data type (although I've not tested ALL data types)
and $v is the cumulative part, the current value of the reduction.
and I'll take the liberty to add another example, as used in my code
<?php
function reduceToTable($html, $p) {
$html .= "<TR><TD><a href=\"$p.html\">$p</a></td>\n";
return $html;
}
$list = Array("page1", "page2", "page3");
$tab = array_reduce($list, "reduceToTable", "<table>\n");
echo $tab . "</table>\n";
?>
hmm, getting stuff on one line sure is tricky, it get's wordwrapped on the char count in html so > counts as 4 chars not one so by the time you've counted "< you've used up 8 chars
If it get's through moderation could someone please make it look ok :)