shuffle for associative arrays, preserves key=>value pairs.
(Based on (Vladimir Kornea of typetango.com)'s function)
<?php
function shuffle_assoc(&$array) {
$keys = array_keys($array);
shuffle($keys);
foreach($keys as $key) {
$new[$key] = $array[$key];
}
$array = $new;
return true;
}
?>
*note: as of PHP 5.2.10, array_rand's resulting array of keys is no longer shuffled, so we use array_keys + shuffle.
PHP - Manual: shuffle
2024-04-19
shuffle
(PHP 4, PHP 5, PHP 7, PHP 8)
shuffle — 打乱数组
说明
shuffle(array
&$array): bool本函数打乱（随机排列单元的顺序）一个数组。 它使用的是伪随机数产生器，并不适合密码学的场合。
参数
-
array -
待操作的数组。
返回值
成功时返回 true， 或者在失败时返回 false。
范例
示例 #1 shuffle() 例子
<?php
$numbers = range(1, 20);
shuffle($numbers);
foreach ($numbers as $number) {
echo "$number ";
}
?>
注释
注意: 此函数为
array中的元素赋与新的键名。这将删除原有的键名，而不是仅仅将键名重新排序。
注意:
重置数组中的内部指针，指向第一个元素。
add a note
User Contributed Notes 16 notes
ahmad at ahmadnassri dot com ¶
12 years ago
andjones at gmail dot com ¶
11 years ago
Shuffle associative and non-associative array while preserving key, value pairs. Also returns the shuffled array instead of shuffling it in place.
<?php
function shuffle_assoc($list) {
if (!is_array($list)) return $list;
$keys = array_keys($list);
shuffle($keys);
$random = array();
foreach ($keys as $key)
$random[$key] = $list[$key];
return $random;
}
?>
Anonymous ¶
12 years ago
I needed a simple function two shuffle a two dimensional array. Please note the second level arrays must be indexed using integers, for example $myarray[0]["Name"] and not $myarray["One"]["Name"]. Here is the function:
<?php
function twodshuffle($array)
{
// Get array length
$count = count($array);
// Create a range of indicies
$indi = range(0,$count-1);
// Randomize indicies array
shuffle($indi);
// Initialize new array
$newarray = array($count);
// Holds current index
$i = 0;
// Shuffle multidimensional array
foreach ($indi as $index)
{
$newarray[$i] = $array[$index];
$i++;
}
return $newarray;
}
?>
Please note it only works on two dimensional arrays. Here is an example:
<?php
$myarray = array("Google" => array("Name" => "Google", "URL" => "www.google.com", "Usage" => "Googling"), "Yahoo" => array("Name" => "Yahoo", "URL" => "www.yahoo.com", "Usage" => "Yahooing?"), "Ask" => array("Name" => "Ask", "URL" => "www.ask.com", "Usage" => "Asking Jeeves"));
print_r(twodshuffle($myarray));
/* And the result is:
Array ( [0] => Array ( [Name] => Ask [URL] => www.ask.com [Usage] => Asking Jeeves ) [1] => Array ( [Name] => Google [URL] => www.google.com [Usage] => Googling ) [2] => Array ( [Name] => Yahoo [URL] => www.yahoo.com [Usage] => Yahooing? ) )
*/
?>
Hope you find it useful!
pineappleclock at gmail dot com ¶
13 years ago
If you want the Power Set (set of all unique subsets) of an array instead of permutations, you can use this simple algorithm:
<?php
/**
* Returns the power set of a one dimensional array,
* a 2-D array.
* array(a,b,c) ->
* array(array(a),array(b),array(c),array(a,b),array(b,c),array(a,b,c))
*/
function powerSet($in,$minLength = 1) {
$count = count($in);
$members = pow(2,$count);
$return = array();
for ($i = 0; $i < $members; $i++) {
$b = sprintf("%0".$count."b",$i);
$out = array();
for ($j = 0; $j < $count; $j++) {
if ($b{$j} == '1') $out[] = $in[$j];
}
if (count($out) >= $minLength) {
$return[] = $out;
}
}
return $return;
}
?>
xzero at elite7hackers dot net ¶
7 years ago
There is an function which uses native shuffle() but preserves keys, and their order, so at end, only values are shuffled.
<?PHP
/**
* Array Quake - Give an array good quake so every value will endup with random given space.
* Keys, and their order are preserved.
* @author xZero <xzero@elite7hackers.net>
* @param array $array
* @return boolean false on failure
*/
function array_quake(&$array) {
if (is_array($array)) {
$keys = array_keys($array); // We need this to preserve keys
$temp = $array;
$array = NULL;
shuffle($temp); // Array shuffle
foreach ($temp as $k => $item) {
$array[$keys[$k]] = $item;
}
return;
}
return false;
}
// Example
$numbers = array(
'ZERO' => 0,
'ONE' => 1,
'TWO' => 2,
'THREE' => 3,
'FOUR' => 4,
'FIVE' => 5,
'SIX' => 6,
'SEVEN' => 7,
'EIGHT' => 8,
'NINE' => 9
);
echo "\nBefore (original):\n";
print_r($numbers);
array_quake($numbers);
echo "\n\nAfter (Array Quake);\n";
print_r($numbers);
echo "\n";
?>
Result example:
Before (original):
Array
(
[ZERO] => 0
[ONE] => 1
[TWO] => 2
[THREE] => 3
[FOUR] => 4
[FIVE] => 5
[SIX] => 6
[SEVEN] => 7
[EIGHT] => 8
[NINE] => 9
)
After (Array Quake);
Array
(
[ZERO] => 4
[ONE] => 2
[TWO] => 0
[THREE] => 8
[FOUR] => 3
[FIVE] => 6
[SIX] => 1
[SEVEN] => 7
[EIGHT] => 5
[NINE] => 9
)
peter at removethisplease dot ddcrew dot com ¶
8 years ago
This seems to do reasonably well as a shuffle() that preserves index assocation:
<?php
function ashuffle (&$arr) {
uasort($arr, function ($a, $b) {
return rand(-1, 1);
});
}
?>
Obviously only works if PHP has closures enabled...
dirk dot avery a t gmail ¶
13 years ago
Building on examples by m227 and pineappleclock, here is a function that returns all permutations of each set in the power set of an array of strings (instead of a string). Thanks for the great examples!
<?php
/*
Use: $arr = power_perms($in);
Example:
$in = array("A","B","C");
$power_perms = power_perms($in);
Returns:
Array
(
[0] => Array
(
[0] => A
[1] => B
[2] => C
)
[1] => Array
(
[0] => A
[1] => C
[2] => B
)
[2] => Array
(
[0] => B
[1] => A
[2] => C
)
[3] => Array
(
[0] => B
[1] => C
[2] => A
)
[4] => Array
(
[0] => C
[1] => A
[2] => B
)
[5] => Array
(
[0] => C
[1] => B
[2] => A
)
[6] => Array
(
[0] => A
[1] => B
)
[7] => Array
(
[0] => B
[1] => A
)
[8] => Array
(
[0] => B
[1] => C
)
[9] => Array
(
[0] => C
[1] => B
)
[10] => Array
(
[0] => A
[1] => C
)
[11] => Array
(
[0] => C
[1] => A
)
[12] => Array
(
[0] => A
)
[13] => Array
(
[0] => B
)
[14] => Array
(
[0] => C
)
)
*/
function power_perms($arr) {
$power_set = power_set($arr);
$result = array();
foreach($power_set as $set) {
$perms = perms($set);
$result = array_merge($result,$perms);
}
return $result;
}
function power_set($in,$minLength = 1) {
$count = count($in);
$members = pow(2,$count);
$return = array();
for ($i = 0; $i < $members; $i++) {
$b = sprintf("%0".$count."b",$i);
$out = array();
for ($j = 0; $j < $count; $j++) {
if ($b{$j} == '1') $out[] = $in[$j];
}
if (count($out) >= $minLength) {
$return[] = $out;
}
}
//usort($return,"cmp"); //can sort here by length
return $return;
}
function factorial($int){
if($int < 2) {
return 1;
}
for($f = 2; $int-1 > 1; $f *= $int--);
return $f;
}
function perm($arr, $nth = null) {
if ($nth === null) {
return perms($arr);
}
$result = array();
$length = count($arr);
while ($length--) {
$f = factorial($length);
$p = floor($nth / $f);
$result[] = $arr[$p];
array_delete_by_key($arr, $p);
$nth -= $p * $f;
}
$result = array_merge($result,$arr);
return $result;
}
function perms($arr) {
$p = array();
for ($i=0; $i < factorial(count($arr)); $i++) {
$p[] = perm($arr, $i);
}
return $p;
}
function array_delete_by_key(&$array, $delete_key, $use_old_keys = FALSE) {
unset($array[$delete_key]);
if(!$use_old_keys) {
$array = array_values($array);
}
return TRUE;
}
?>
Antonio Ognio ¶
14 years ago
Another shuffle() implementation that preserves keys, does not use extra memory and perhaps is a bit easier to grasp.
<?php
if (function_exists('shuffle_with_keys')===false) {
function shuffle_with_keys(&$array) {
/* Auxiliary array to hold the new order */
$aux = array();
/* We work with an array of the keys */
$keys = array_keys($array);
/* We shuffle the keys */
shuffle($keys);
/* We iterate thru' the new order of the keys */
foreach($keys as $key) {
/* We insert the key, value pair in its new order */
$aux[$key] = $array[$key];
/* We remove the element from the old array to save memory */
unset($array[$key]);
}
/* The auxiliary array with the new order overwrites the old variable */
$array = $aux;
}
}
?>
rick at suggestive dot com ¶
12 years ago
Many people in SEO need to supply an array and shuffle the results and need the same result each time that page is generated. This is my implementation with a working example:
<?php
function seoShuffle(&$items,$string) {
mt_srand(strlen($string));
for ($i = count($items) - 1; $i > 0; $i--){
$j = @mt_rand(0, $i);
$tmp = $items[$i];
$items[$i] = $items[$j];
$items[$j] = $tmp;
}
}
$items = array('one','two','three','four','five','six');
$string = 'whatever';
echo '<pre>';
print_r($items);
echo '</pre>';
seoShuffle($items,$string);
echo '<pre>';
print_r($items);
echo '</pre>';
?>
sivaji2009 at gmail dot com ¶
13 years ago
Here i wrote a custom shuffle function which preserves the array index and distributes the array element randomly.
<?php
/*
* return an array whose elements are shuffled in random order.
*/
function custom_shuffle($my_array = array()) {
$copy = array();
while (count($my_array)) {
// takes a rand array elements by its key
$element = array_rand($my_array);
// assign the array and its value to an another array
$copy[$element] = $my_array[$element];
//delete the element from source array
unset($my_array[$element]);
}
return $copy;
}
$array = array(
'a' => 'apple',
'b' => 'ball',
'c' => 'cat',
'd' => 'dog',
'e' => 'egg',
'f' => 'fan',
'g' => 'gun'
);
print_r(custom_shuffle($array));
Array
(
[c] => cat
[e] => egg
[f] => fan
[a] => apple
[b] => ball
[g] => gun
[d] => dog
)
?>
Eric Anderson ¶
11 years ago
Copy and paste this script and refresh the page to see the shuffling effect.
<?php
/**
* Shuffles and displays cards in a deck
* @author: Eric Anderson
* @filename: deckofcards.php
*/
// Create an array of face values
// and an array of card values
// then merge them together
$cards = array_merge(array("J", "Q", "K", "A"), range(2,10)); // 13 cards
// Shuffle the cards
shuffle($cards);
// Create an multidimentional array to hold the 4 suits
$suits = array(
'Heart' => array(),
'Spade' => array(),
'Diamond' => array(),
'Club' => array()
);
// Add cards to their respective suits
for($i = 0; $i < count($suits); $i++)
{
for($j = 0; $j < count($cards); $j++)
{
$suits['Heart'][$j] = $cards[$j]."<span style=color:#FF0000;>♥</span>";
$suits['Spade'][$j] = $cards[$j]."♠";
$suits['Diamond'][$j] = $cards[$j]."<span style=color:#FF0000;>♦</span>";
$suits['Club'][$j] = $cards[$j]."♣";
}
}
// Create a deck
$deck = array();
// Merge the suits into the empty deck array
$deck = array_merge($deck, $suits);
// Display the deck to the screen
echo "<p><b>Deck of cards:</b></p>";
foreach($deck as $k1 => $v1)
{
// Display suit name
echo "<p> $k1's<br /> {<br />  ";
$acc = 0;
// Display card value
foreach($v1 as $k2 => $v2)
{
echo "$v2 ";
$acc++;
if ($acc == 4)
{
echo "<br />  ";
$acc = 0;
}
}
echo "<br /> }</p>";
}
?>
aalaap at gmail dot com ¶
13 years ago
I've been wondering why shuffle() doesn't provide the shuffled array as a return value instead of a bool. I mean, what could possibly go wrong in shuffling elements from an array?
So I use something like this:
<?php
function array_shuffle($array) {
if (shuffle($array)) {
return $array;
} else {
return FALSE;
}
}
?>
ezakto at ezakto dot com ¶
11 years ago
This is a replica of shuffle() but preserving keys (associative and non-associative)
bool kshuffle ( array &$array )
<?php
function kshuffle(&$array) {
if(!is_array($array) || empty($array)) {
return false;
}
$tmp = array();
foreach($array as $key => $value) {
$tmp[] = array('k' => $key, 'v' => $value);
}
shuffle($tmp);
$array = array();
foreach($tmp as $entry) {
$array[$entry['k']] = $entry['v'];
}
return true;
}
$array = array('first' => 0, 'second' => 1, 'third' => 2);
kshuffle($array);
print_r($array); // [second] => 1 [first] => 0 [third] => 2
$array = array('first', 'second', 'third');
kshuffle($array);
print_r($array); // [1] => second [2] => third [0] => first
?>
tony at brokerbin dot com ¶
13 years ago
Here is IMO the simplest and extremely fast way to shuffle an associative array AND keep the key=>value relationship. However, it ONLY works if there are NO NUMERIC keys AT ALL. Look into array_merge for the reason why.
<?php
$unshuffled = array('one'=>1,'two'=>2,'three'=>3);
$shuffled = array_merge( array_flip(array_rand($unshuffled,count($unshuffled))),$unshuffled );
?>
peace
DiosDe ¶
11 months ago
implementation of shuffle() using random_int()
<?php
function random_int_shuffle ( array $array ): array
{
$array = array_values($array);
$result = [];
$skip_indexes = [];
$sizeof_array = count($array);
for ( $i = 0; $i < $sizeof_array; $i++ )
{
do
{
$random_index = random_int(0, $sizeof_array);
} while ( in_array($random_index, $skip_indexes) );
$skip_indexes[] = $random_index;
$result[] = $array[$random_index];
}
return $result;
}
?>
tyler at CompLangs dot com ¶
12 years ago
Here is a quick function I wrote that generates a random password and uses shuffle() to easily shuffle the order.
<?php
public function randPass($upper = 3, $lower = 3, $numeric = 3, $other = 2) {
//we need these vars to create a password string
$passOrder = Array();
$passWord = '';
//generate the contents of the password
for ($i = 0; $i < $upper; $i++) {
$passOrder[] = chr(rand(65, 90));
}
for ($i = 0; $i < $lower; $i++) {
$passOrder[] = chr(rand(97, 122));
}
for ($i = 0; $i < $numeric; $i++) {
$passOrder[] = chr(rand(48, 57));
}
for ($i = 0; $i < $other; $i++) {
$passOrder[] = chr(rand(33, 47));
}
//randomize the order of characters
shuffle($passOrder);
//concatenate into a string
foreach ($passOrder as $char) {
$passWord .= $char;
}
//we're done
return $passWord;
}
?>
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