shuffle

    (PHP 4, PHP 5, PHP 7, PHP 8)

    shuffle — Mezcla un array

    Descripción

    shuffle(array &$array): bool

    Esta función mezcla un array (crea un orden aleatorio de sus elementos). Utiliza un generador de números seudoaleatorios que no es apto para fines criptográficos.

    Nota:

    Si dos miembros se comparan como iguales, su orden relativo en el array oredenado será indefinido.

    Parámetros

    array

    El array.

    Valores devueltos

    Devuelve true en caso de éxito o false en caso de error.

    Ejemplos

    Ejemplo #1 Ejemplo de shuffle()

    <?php
    $números     = range(1, 20);
    shuffle($números);
    foreach (    $números as $número) {
    echo     "$número ";
    }
    ?>

    Notas

    Nota: Esta función asigna nuevas clave a los elemenos del array. Eliminará cualquier clave existente que haya sido asignada, en lugar de reordenar las claves.

    Ver también

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    User Contributed Notes 16 notes

    up
    131
    ahmad at ahmadnassri dot com
    14 years ago
    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.
    up
    26
    andjones at gmail dot com
    14 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;
    }

    ?>
    up
    7
    Anonymous
    15 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!
    up
    9
    dirk dot avery a t gmail
    15 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;
    }
    ?>
    up
    4
    pineappleclock at gmail dot com
    15 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;
    }
    ?>
    up
    6
    peter at removethisplease dot ddcrew dot com
    10 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...
    up
    2
    xzero at elite7hackers dot net
    9 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
    )
    up
    3
    tony at brokerbin dot com
    16 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
    up
    4
    aalaap at gmail dot com
    15 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;
    }
    }
    ?>
    up
    2
    ezakto at ezakto dot com
    14 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

    ?>
    up
    3
    rick at suggestive dot com
    14 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>';
    ?>
    up
    2
    sivaji2009 at gmail dot com
    15 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
    )

    ?>
    up
    2
    Eric Anderson
    13 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;>&hearts;</span>";
    $suits['Spade'][$j] = $cards[$j]."&spades;";
    $suits['Diamond'][$j] = $cards[$j]."<span style=color:#FF0000;>&diams;</span>";
    $suits['Club'][$j] = $cards[$j]."&clubs;";
    }
    }

    // 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 => $v1)
    {
    // Display suit name
    echo "<p>&emsp;$k1's<br />&emsp;{<br />&emsp;&emsp;";
    $acc = 0;

    // Display card value
    foreach($v1 as $k2 => $v2)
    {
    echo     "$v2&nbsp";
    $acc++;

    if (    $acc == 4)
    {
    echo     "<br />&emsp;&emsp;";
    $acc = 0;
    }
    }
    echo     "<br />&emsp;}</p>";
    }
    ?>
    up
    2
    tyler at CompLangs dot com
    14 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;
    }
    ?>
    up
    1
    Antonio Ognio
    16 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;
    }
    }
    ?>
    up
    0
    DiosDe
    3 years 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;
    }
    ?>
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