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shuffle

(PHP 4, PHP 5, PHP 7)

shuffle — 将数组打乱

说明

bool shuffle ( array &$array )

本函数打乱（随机排列单元的顺序）一个数组。

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

Example #1 shuffle() 例子

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

更新日志

版本	说明
4.2.0	随机数发生器自动进行播种。

注释

Note: 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。

参见

数组排序函数对比

用户评论:

[#1] xzero at elite7hackers dot net [2015-05-30 13:09:02]

There is an function which uses native shuffle() but preserves keys, and their order, so at end, only values are shuffled.

<?PHP 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
)

[#2] peter at removethisplease dot ddcrew dot com [2013-12-02 13:55:22]

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...

[#3] timtrinidad at gmail dot com [2011-08-08 12:38:32]

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.

[#4] Eric Anderson [2011-03-29 09:33:55]

Copy and paste this script and refresh the page to see the shuffling effect.

<?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]."&hearts;"; $suits['Spade'][$j] = $cards[$j]."&spades;"; $suits['Diamond'][$j] = $cards[$j]."&diams;"; $suits['Club'][$j] = $cards[$j]."&clubs;"; } } // Create a deck $deck = array(); // Merge the suits into the empty deck array $deck = array_merge($deck, $suits); // Display the deck to the screen echo "Deck of cards:"; foreach($deck as $k1 => $v1) { // Display suit name echo "&emsp;$k1's &emsp;{ &emsp;&emsp;"; $acc = 0; // Display card value foreach($v1 as $k2 => $v2) { echo "$v2&nbsp"; $acc++; if ($acc == 4) { echo " &emsp;&emsp;"; $acc = 0; } } echo " &emsp;}"; } ?>

[#5] andjones at gmail dot com [2010-08-26 21:35:10]

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; } ?>

[#6] ezakto at ezakto dot com [2010-07-24 23:13:38]

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 ?>

[#7] m0gr14 at gmail dot com [2010-07-04 10:39:37]

This function shuffles an associative array recursive.

<?php 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>'; ?>

[#8] rick at suggestive dot com [2010-03-24 14:19:04]

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>'; ?>

[#9] tyler at CompLangs dot com [2010-01-01 18:59:46]

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; } ?>

[#10] ahmad at ahmadnassri dot com [2009-11-18 20:58:12]

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.

[#11] Anonymous [2009-08-28 09:18:52]

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)); ?>

Hope you find it useful!

[#12] aalaap at gmail dot com [2009-06-08 05:12:36]

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; } } ?>

[#13] sivaji2009 at gmail dot com [2009-05-17 14:07:54]

Here i wrote a custom shuffle function which preserves the array index and distributes the array element randomly.

<?php 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 ) ?>

[#14] dirk dot avery a t gmail [2009-04-30 08:58:42]

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 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; } ?>

[#15] pineappleclock at gmail dot com [2009-01-22 10:06:30]

If you want the Power Set (set of all unique subsets) of an array instead of permutations, you can use this simple algorithm:

<?php 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; } ?>

[#16] tony at brokerbin dot com [2008-11-11 19:26:06]

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

[#17] Antonio Ognio [2008-05-06 09:42:45]

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) { $aux = array(); $keys = array_keys($array); shuffle($keys); foreach($keys as $key) { $aux[$key] = $array[$key]; unset($array[$key]); } $array = $aux; } } ?>

[#18] [2006-06-07 14:53:04]

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 } ?>

[#19] bill at SWScripts dot com [2005-09-22 09:45:55]

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.