SunshinePHP Developer Conference 2015

shuffle

(PHP 4, PHP 5)

shuffleShuffle an array

Descrierea

bool shuffle ( array &$array )

This function shuffles (randomizes the order of the elements in) an array.

Parametri

array

The array.

Valorile întoarse

Întoarce valoarea TRUE în cazul succesului sau FALSE în cazul eșecului.

Exemple

Example #1 shuffle() example

<?php
$numbers 
range(120);
shuffle($numbers);
foreach (
$numbers as $number) {
    echo 
"$number ";
}
?>

Note

Notă: Această funcție atribuie chei noi elementelor din array. Ea va elimina cheile existente, care posibil au fost atribuite, în loc doar să rearanjeze cheile.

Vedeți de asemenea

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User Contributed Notes 18 notes

up
31
ahmad at ahmadnassri dot com
4 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
8
andjones at gmail dot com
4 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
4
dirk dot avery a t gmail
5 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;
}
?>
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4
Eric Anderson
3 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
3
pineappleclock at gmail dot com
5 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
4
Anonymous
5 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
1
aalaap at gmail dot com
5 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
bill at SWScripts dot com
9 years ago
Just a quick note to let people know that shuffle() will work on multidimensional associative arrays provided that the first key is already numeric.

So this array can be shuffled without losing any of the secondary keys or their values:

$array[0]['color'], $array[0]['size'], $array[0]['fabric']
. . .
$array[50]['color'], $array[50]['size'], $array[50]['fabric']

I recently ran up against needing to randomize this array and tried shuffle even though it's not really for associative arrays.

Hope it helps somebody out there.
up
1
Anonymous
8 years ago
Posted below is code that you would expect to work

<?php

$keys
= shuffle(array_keys($arr));

foreach (
$keys as $key) {

 
$arr_elem = $arr[$key];
 
// do what you want with the array element

}

?>

This in fact does not work because shuffle returns a boolean true or false. More accurate code using this method would be:

<?php

$keys
= array_keys($arr);
shuffle($keys);

foreach (
$keys as $key) {

 
$arr_elem = $arr[$key];
 
// do what you want with the array element

}

?>
up
3
tyler at CompLangs dot com
4 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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1
timtrinidad at gmail dot com
3 years ago
It appears that the suhosin extensions >= 0.9.26 that have the suhosin.mt_srand.ignore and suhosin.srand.ignore settings set to "Off" do not affect shuffle().

In other words, the only way I was able to get pseudo-random and predictable results through shuffle() was to disable the extension.
up
1
sivaji2009 at gmail dot com
5 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
1
tony at brokerbin dot com
5 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
1
Antonio Ognio
6 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;
  }
}
?>
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1
rick at suggestive dot com
4 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
1
peter at removethisplease dot ddcrew dot com
10 months 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
0
ezakto at ezakto dot com
4 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
0
m0gr14 at gmail dot com
4 years ago
This function shuffles an associative array recursive.

<?php

/**
* Shuffles an associative array recursive
* @author Mogria <m0gr14@gmail.com>
* @param array $array
* @return array
*
*/

function rec_assoc_shuffle($array)
{
 
$ary_keys = array_keys($array);
 
$ary_values = array_values($array);
 
shuffle($ary_values);
  foreach(
$ary_keys as $key => $value) {
    if (
is_array($ary_values[$key]) AND $ary_values[$key] != NULL) {
     
$ary_values[$key] = rec_assoc_shuffle($ary_values[$key]);
    }
   
$new[$value] = $ary_values[$key];
  }
  return
$new;
}

?>

Example of use:
<?php
$array
=
    Array(
       
1,
        Array(
           
1,
           
2,
           
3,
           
4,
            Array(
               
1,
               
2,
               
3,
               
4,
               
5
           
)
        ),
       
2,
       
3,
        Array(
           
0,
           
1,
                Array(
                   
1,
                   
2,
                   
3,
                   
4,
                        Array(
                           
1,
                           
6,
                           
5,
                           
2,
                           
1,
                           
3
                       
)
                )
        ),
       
4,
       
5,
       
6,
       
7
   
);
$array = rec_assoc_shuffle($array);
echo
'<pre>';
print_r($array);
echo
'</pre>';

/*
Returns:
Array
(
    [0] => 6
    [1] => 5
    [2] => Array
        (
            [0] => 1
            [1] => 3
            [2] => Array
                (
                    [0] => 3
                    [1] => 1
                    [2] => 2
                    [3] => 4
                    [4] => 5
                )

            [3] => 2
            [4] => 4
        )

    [3] => 3
    [4] => Array
        (
            [0] => Array
                (
                    [0] => 3
                    [1] => 1
                    [2] => 4
                    [3] => Array
                        (
                            [0] => 5
                            [1] => 1
                            [2] => 3
                            [3] => 6
                            [4] => 1
                            [5] => 2
                        )

                    [4] => 2
                )

            [1] => 1
            [2] => 0
        )

    [5] => 2
    [6] => 1
    [7] => 4
    [8] => 7
)

*/

?>
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