I am new to this php. I only edit the codes according to my requirement.I displayed a random list of words in two sets with 15 in each set.
Below is the code for that.
<?php
srand((float) microtime() * 10000000);
$input = array(
'Art Of Betrayal', 'California Or Bust', 'Flood Gate','Bomb Shell','Dark Town','Kylies Smiley','song1',
'song50', 'song1', 'song57', 'Dark Town', 'song47', 'song61', 'song56', 'Kylies Smiley', 'song22','song50', 'song1', 'song57', 'Dark Town', 'song47', 'song61', 'song56', 'Kylies Smiley','song50', 'song1', 'Dark Town', 'song57', 'song54', 'song47', 'song61', 'song56', 'song49', 'Kylies Smiley', 'song53', 'song58');
?>
<table border="1" cellpadding="0" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" width="100%" id="AutoNumber3">
<tr>
<td width="50%" align="center">SET1</td>
<td width="50%" align="center">SET2</td>
</tr>
<?php
for ($i = 0; $i<sizeof($input);$i++)
{
$rand_keys = array_rand($input,5);
if ($i!=30)
{
?>
<tr>
<td width="50%" align="center">
<?php echo $input[$rand_keys[0]] . "\n <br />" ;?></td>
<td width="50%" align="center">
<?php echo $input[$rand_keys[1]] . "\n <br />" ;?> </td></tr>
<?php
}
else
{?>
</table>
<?php break;
}
}
?>
array_rand
(PHP 4, PHP 5)
array_rand — 配列から一つ以上の要素をランダムに取得する
説明
mixed array_rand ( array $input [, int $num_req] )array_rand() は、 配列から一つ以上のランダムなエントリを取得しようとする場合に有用です。 この関数は、配列 input およびオプションとして num_req を引数とします。 この引数は、取得するエントリの数を指定します。 指定されない場合は、デフォルトの 1 になります。
エントリを一つだけ取得する場合、 array_rand() はランダムなエントリのキーを返します。 その他の場合は、ランダムなエントリのキーの配列を返します。 これにより、ランダムなキーを取得し、 配列から値を取得することが可能になります。
注意: PHP 4.2.0 以降、 srand() または mt_srand() によりランダム数生成器にシードを与える必要はありません。 これは、この処理が自動的に行われるためです。
例 268. array_rand() の例
<?php
srand((float) microtime() * 10000000);
$input = array("ネオ", "モーフィアス", "トリニティ", "サイファー", "タンク");
$rand_keys = array_rand($input, 2);
echo $input[$rand_keys[0]] . "\n";
echo $input[$rand_keys[1]] . "\n";
?>
shuffle() も参照ください。
array_rand
bharan_n at yahoo dot co dot in
25-Aug-2007 09:00
25-Aug-2007 09:00
Hayley Watson
12-Jun-2007 12:38
12-Jun-2007 12:38
To add to asp at cyberlin dot eu's comment. Not only will it return NULL but it will also trigger a warning, and not only if the number of elements requested is too large to be satisfied by the array but also if it is zero. The warning message sums the situation up: "Second argument has to be between 1 and the number of elements [inclusive] in the array".
asp at cyberlin dot eu
13-Apr-2007 05:24
13-Apr-2007 05:24
array_rand() is very useful, but note:
In the case that the count of the array is smaller then the optional parameter 'num_req', it will return an empty array (or string).
Reinoud Elhorst
10-Apr-2007 07:50
10-Apr-2007 07:50
Please note that (at least in PHP 4.3.11), while each key from the source array has a equal chance of being picked, the order in which they are returned is NOT random. In an array with keys from one to 10, where 2 random keys are picked, 0 is picked as the first number 18.8% of the time, and only as second number in 1.1% of the time:
$n=100000;
$a=array(1,2,3,4,5,6,7,8,9,10);
$b=array();
for($i=0;$i<sizeof($a);$i++) {
$b[$i]=array(0,0);
}
for($i=0;$i<$n;$i++) {
$keys=array_rand($a,2);
$b[$keys[0]][0]++;
$b[$keys[1]][1]++;
}
for ($i=0;$i<sizeof($b);$i++){
printf("%d: %04.1f%% %04.1f%% %04.1f%%", $i, ($b[$i][0]/$n*100),($b[$i][1]/$n*100),($b[$i][0]+$b[$i][1])/$n*100);
}
The result is:
0: 18.8% 01.1% 19.9%
1: 17.0% 03.3% 20.3%
2: 14.3% 05.7% 20.0%
3: 12.2% 07.9% 20.1%
4: 10.0% 10.0% 20.0%
5: 07.8% 12.0% 19.8%
6: 05.5% 14.5% 20.0%
7: 03.3% 16.6% 19.9%
8: 01.2% 18.9% 20.1%
9: 10.0% 09.9% 19.9%
The workaround is adding a shuffle command to shuffle the keys:
0: 10.0% 10.0% 20.0%
1: 10.0% 10.0% 20.0%
2: 10.0% 10.0% 20.0%
3: 10.0% 10.0% 20.0%
4: 10.0% 10.0% 20.0%
5: 10.0% 10.0% 20.0%
6: 10.1% 10.0% 20.1%
7: 10.0% 10.0% 20.0%
8: 10.0% 10.0% 20.0%
9: 10.0% 10.0% 20.0%
Sven Arduwie
29-Jan-2007 10:40
29-Jan-2007 10:40
Here is my array_mt_rand function.
<?php
function array_mt_rand(array $array, $numberOfKeys = 1)
{
if (!is_int($numberOfKeys)) throw new Exception;
if ($numberOfKeys < 1) throw new Exception;
$keys = array_keys($array);
$maximum = count($array) - 1;
if ($numberOfKeys == 1) {
return $keys[mt_rand(0, $maximum)];
} else {
$randomKeys = array();
for ($i = 0; $i < $numberOfKeys; $i++) {
$randomKeys[] = $keys[mt_rand(0, $maximum)];
}
return $randomKeys;
}
}
?>
Frederick Lemasson aka djassper at gmail
04-Dec-2006 05:57
04-Dec-2006 05:57
To select a random Value (not a Key) from a Multi-Dimentionnal array I made a recursive function : array_multi_rand()
the following exemple randomly selects an url from a multidimentionnal array :
<?
$Expos['Google']['Science']='news.google.fr/news?topic=t';
$Expos['Google']['Economie']='news.google.fr/news?topic=b';
$Expos['Google']['Sante']='news.google.fr/news?topic=m';
$Expos['Yahoo']='fr.news.yahoo.com';
$Expos['Events']['LogicielLibre']='agendadulibre.org';
$Expos['MyBlog']='www.kik-it.com';
function array_multi_rand($Zoo){
$Boo=array_rand($Zoo);
if(is_array($Zoo[$Boo])){
return array_multi_rand($Zoo[$Boo]);
}else{
return $Zoo[$Boo];
}
}
echo(array_multi_rand($Expos));
?>
jan at planetromeo dot com
25-Nov-2006 01:56
25-Nov-2006 01:56
Instead of using the horrible slow
select * from some_table order by rand() limit 1;
have a look at this more performant solution from
http://jan.kneschke.de/projects/mysql/order-by-rand/
SELECT * FROM some_table AS r1
JOIN (SELECT ROUND(RAND() * (SELECT MAX(id) FROM some_table)) AS id) AS r2
WHERE r1.id >= r2.id
ORDER BY r1.id ASC
LIMIT 1;
alec
11-Nov-2006 10:37
11-Nov-2006 10:37
select * from some_table order by rand() limit 1;
is extremely slow for large tables. large as in a a few thousand entries.
dbrooks at icarusstudios dot com
06-Sep-2006 06:28
06-Sep-2006 06:28
Instead of looping through all the rows selected to pick a random one, let the server do the work for you:
select * from some_table order by rand() limit 1;
JS
04-Sep-2006 07:07
04-Sep-2006 07:07
I wanted to write something that picks a random entry from a 1column-MySQL database - simply Post Of The Moment (potm). I know there surly are many better ways to do it, but I`m rather new to PHP :) Anyway, it`s simple and no-problem working code.
Of course I assume your DB exists and you always have something in it.
@$link = MySQL_Connect("localhost", "username", "password"); //connect to mysql
mySQL_Select_DB("database"); //..to DB
@$potms = MySQL_Query("SELECT * FROM potm"); //now we get all from our table and store it
MySQL_Close($link); //there`s no need for connection, so we should close it
$potm_array = ''; //sets variables to "zero" values
$i = 0;
while ($entry = MySQL_Fetch_Array($potms)) //now we go through our DB
{
$potm_array[$i] = $entry; //our temporary array from which we will random pick a field key
$i++; //now we increment our field key
}
$potm_id = array_rand($potw_array); //picks a random key from array
$potm = $potm_array[$potm_id]['name_of_the_field']; //now we have stored our Post Of The Moment in $potm
..hope this helps
mark at rugbyweb dot org
30-Aug-2006 05:29
30-Aug-2006 05:29
I was setting up a rotating add banner and was trying to find a way to go about it using an auto_increment id from the database, so I wrote this little script:
<?php
require "mysql.php";
global $c;
print "<center>";
$qq=mysql_query("SELECT adID FROM ads WHERE adCLICKS<=adMAX",$c) or die (mysql_error()."<br>Error, please report this error quoting #QAB");
while($q=mysql_fetch_array($qq))
{
$ad1[$q['adID']]++; //Used an array and inserted the database query results into it.
}
$ad=array_rand($ad1, 1); //Did a random array function and then used it in the query below.
$er=mysql_query("SELECT * FROM ads WHERE adID='$ad'") or die (mysql_error()."<br>Error, please report this error quoting #QAB3");
if(!mysql_num_rows($er))
{
print "<A href='advertise.php'>Place an ad here!</a>";
exit;
}
$r=mysql_fetch_array($er);
print "<a href='adsout.php?ID={$r['adID']}&BLOCK=1'><img src='{$r['adAD']}' alt='{$r['adNAME']}' height='60' width='468'></a>";
?>
dragonfly at dragonflyeye dot net
08-Jul-2006 05:28
08-Jul-2006 05:28
Well, I came up with a workaround for my earlier problem. For those of you who might need to shuffle around multi-dimensional arrays (I used this to randomize a list of headlines from a MySQL database query), here's what I did to get the desired output:
$subs = //my query went here
$shfl = array_rand($subs, 5);
$shsubs = array();
for ($x=0; $x<count($shfl); $x++) {
$shsubs[] = $subs[$shfl[$x]];
}
There may in fact be a much easier way to do this, but this is what I came up with and its working!
Thanks to everyone that makes php.net the invaluable tool for us nooobies!
dragonfly at dragonflyeye dot net
07-Jul-2006 11:57
07-Jul-2006 11:57
Well, this is interesting. I don't see anyone else commenting on this, so just in case you were planning to use this function like I was, be prepared: array_rand does not handle multidimensional arrays. It just ends up returning a list of the X-axis values without the Y-axis arrays. Bummer. I'm going to have to find another way to do what I wanted.
steve at webcommons dot biz
06-Jul-2006 06:12
06-Jul-2006 06:12
Following are functions for getting a random key or value (or array of random keys or values) from a filtered array. In other words, given an array of data, these functions filter out what you don't want, then extract a random element or bunch from what's left.
$CallBack is the filtering function.
// Utility function for functions below
function GetRandomArrayValue($TheArray) {
return $TheArray[array_rand($TheArray)];
}
// Get a random key or array of keys from a filtered array
function GetRandomFilteredArrayKeys($aInput, $CallBack = NULL, $NumReq = 1) {
$FilteredKeys = array_keys(array_filter($aInput, $CallBack));
if ($NumReq <= 1) {
return GetRandomArrayValue($FilteredKeys);
}
else {
shuffle($FilteredKeys);
return array_slice($FilteredKeys, 0, $NumReq);
}
}
// Get a random value or array of values from a filtered array
function GetRandomFilteredArrayValues($aInput, $CallBack = NULL, $NumReq = 1) {
$aFiltered = array_filter($aInput, $CallBack);
if ($NumReq <= 1) {
return $aFiltered[GetRandomArrayValue(array_keys($aFiltered))];
}
else {
shuffle($aFiltered);
return array_slice($aFiltered, 0, $NumReq);
}
}
trukin at gmail dot com
17-Mar-2006 06:23
17-Mar-2006 06:23
Modify of last note:
<?php
if (!function_exists('array_rand')) {
function array_rand($array, $lim=1) {
mt_srand((double) microtime() * 1000000);
for($a=0; $a<=$lim; $a++){
$num[] = mt_srand(0, count($array)-1);
}
return @$num;
}
}
?>
mt_rand generates a better random number, and with the limit.
emailfire at gmail dot com
13-Mar-2006 06:32
13-Mar-2006 06:32
<?php
if (!function_exists('array_rand')) {
function array_rand($array) {
srand((double) microtime() * 1000000);
return rand(0, count($array)-1);
}
}
?>
Will-ster
02-Jan-2006 09:18
02-Jan-2006 09:18
This is something I have been playing with for quite awhile. I'm very new to php, but i finally got it to work. it's a function that will take and array[$arrquo] and find a particular keyword[$find] in the different elements of the array then take those elements that posess that keyword and display them at random
<?php
function popbyword($arrquo,$find)
{
$newarr = array('');
foreach($arrquo as $line)
{
if( strstr( $line, $find ) )
{
array_push($newarr, $line);
}
}
srand((double)microtime()*1000000);
$rquote = array_rand($newarr);
echo $newarr[$rquote];
}
popbyword($images, 'Albert');
?>
In my case I had this huge array of quotes with 90 some elements. I was able to find certain keywords in those elements then ONLY display the elements that had those keywords. NEAT! Maybe only because I'm new.
farooqym at ieee dot org
01-Jan-2006 07:05
01-Jan-2006 07:05
Here's an algorithm to make a weighted selection of an item from an array.
Say we have an array $items with keys as items and values as corresponding weights.
For example:
<?php
$items = array(
item1 => 3,
item2 => 4,
item3 => 5,
);
?>
i.e. we want to choose item1 25% of the time, item2 33.3% of the time and item3 41.6% of the time.
Here's a function that works when the weights are positive integers:
<?php
function array_rand_weighted($values) {
$r = mt_rand(1, array_sum($values));
foreach ($values as $item => $weight) {
if ($r <= $weight) return $item;
$r -= $weight;
}
}
?>
Enjoy!
bjcffnet at gmail dot com
30-Aug-2005 08:29
30-Aug-2005 08:29
As wazaawazaa600 at msn dot com pointed out, a multi-dimensional array doesn't work with this function. So, I hope I can help someone with this :)
<?php
/**
* Returns a number of random elements from an array.
*
* It returns the number (specified in $limit) of elements from
* $array. The elements are returned in a random order, exactly
* as it was passed to the function. (So, it's safe for multi-
* dimensional arrays, aswell as array's where you need to keep
* the keys)
*
* @author Brendan Caffrey <bjcffnet at gmail dot com>
* @param array $array The array to return the elements from
* @param int $limit The number of elements to return from
* the array
* @return array The randomized array
*/
function array_rand_keys($array, $limit = 1) {
$count = @count($array)-1;
// Sanity checks
if ($limit == 0 || !is_array($array) || $limit > $count) return array();
if ($count == 1) return $array;
// Loop through and get the random numbers
for ($x = 0; $x < $limit; $x++) {
$rand = rand(0, $count);
// Can't have double randoms, right?
while (isset($rands[$rand])) $rand = rand(0, $count);
$rands[$rand] = $rand;
}
$return = array();
$curr = current($rands);
// I think it's better to return the elements in a random
// order, which is why I'm not just using a foreach loop to
// loop through the random numbers
while (count($return) != $limit) {
$cur = 0;
foreach ($array as $key => $val) {
if ($cur == $curr) {
$return[$key] = $val;
// Next...
$curr = next($rands);
continue 2;
} else {
$cur++;
}
}
}
return $return;
}
?>
alexkropivko at(dog) yandex dot ru
16-Jun-2005 10:21
16-Jun-2005 10:21
There was a mistake at "Paul Hodel (paul at ue dot com dot br) 17-Apr-2003 04:40":
String
echo $new_input = $input[$v];
have to be:
echo $new_input[] = $input[$v];
maxnamara at yahoo dot com
13-Mar-2005 08:22
13-Mar-2005 08:22
<?php
$input = array("Neo", "Morpheus", "Trinity", "Cypher", "Tank");
function my_array_rand($input,$i=2){
srand((float) microtime() * 10000000);
$rand_keys = array_rand($input, $i);
/*
print $input[$rand_keys[0]] . "\n";
print $input[$rand_keys[1]] . "\n";
*/
$res = array();
if($i > 1){
for($a=0;$a<$i;$a++){
$res[] = $input[$rand_keys[$a]];
}
}
else{
$res[] = $input[$rand_keys];
}
return $res;
}
$a = my_array_rand($input,3);
echo "<pre>";
print_r($a);
echo "</pre>";
?>
yhoko at yhoko dot com
28-Aug-2004 10:16
28-Aug-2004 10:16
According to office at at universalmetropolis dot com I have to say that the example is wrong.
<?php
// retrieve one of the options at random from the array
$teamcolours = $teamcolours[rand(0,count($teamcolours))];
?>
The count() function will return the number of items in the array, that's the last index + 1. So if there's 2 items in the array, count() will return 2 but the indices are 0 and 1. Now since rand(x,y) randomizes between x and y inclusively the index from the above example may be out of bounds. Thus you have to subtract 1 from the count:
<?php
// Get random item
$teamcolours = $teamcolours[rand(0,count($teamcolours)-1)];
?>
leighm at linuxbandwagon dot com leigh morresi
09-Mar-2004 12:36
09-Mar-2004 12:36
Another array based password generator, this one is a port from the python mailman version.
this generates slightly predictable but human readable passwords that people can remember
output passwords are for example "rikanumi"
<?php
// port of mailman version
function MakeRandomPassword($length=6) {
$_vowels = array ('a', 'e', 'i', 'o', 'u');
$_consonants = array ('b', 'c', 'd', 'f', 'g', 'h', 'k', 'm', 'n','p', 'r', 's', 't', 'v', 'w', 'x', 'z');
$_syllables = array ();
foreach ($_vowels as $v) {
foreach ($_consonants as $c) {
array_push($_syllables,"$c$v");
array_push($_syllables,"$v$c");
}
}
for ( $i=0;$i<=($length/2);$i++) $newpass=$newpass.$_syllables[array_rand($_syllables) ];
return $newpass;
?>
}
tim dot meader at gsfc dot nasa dot gov
06-Mar-2004 11:31
06-Mar-2004 11:31
Just thought I would contribute a password generation function
that uses array_rand. I wrote this because I
could not find anywhere a PHP equivalent of the ability
that the String::Random module in Perl has, which allows
you to specify a schema for how you want the random
string created. In other words: I want 2 Uppercase, 3
lowercase, 2 intergers...etc. This isn't too comprehensive,
notably it doesn't account for one choosing more itterations
of a particular type than there are in the array (ie -
choosing more than 10 numbers from output). Additionally,
this doesn't allow for any repeated characters. Hope it can
be of use... comments appreciated.
<?php
function &doGeneratePasswords()
{
//////////////////////////////////////
// lowercase L left out for clarity //
//////////////////////////////////////
$l_achLowercase = array("a","b","c","d","e","f","g","h",
"i","j","k","m","n","o","p","q",
"r","s","t","u","v","w","x",
"y","z");
$l_iNumLowercase = count($l_achLowercase);
////////////////////////////////////////////
// uppercase I and O left out for clarity //
////////////////////////////////////////////
$l_achUppercase = array("A","B","C","D","E","F","G","H",
"J","K","L","M","N","P","Q",
"R","S","T","U","V","W",
"X","Y","Z");
$l_iNumUppercase = count($l_achUppercase);
$l_aiNumbers = array("1","2","3","4","5","6","7","8","9","0");
$l_iNumNumbers = count($l_aiNumbers);
$l_achSpecialChars = array("!","#","%","@","*","&");
$l_iNumSpecialChars = count($l_achSpecialChars);
///////////////////////////////////////////////////////////////////
// Make sure to create enough blank spaces as you want passwords //
///////////////////////////////////////////////////////////////////
$l_astPasswds = array("","","","");
//////////////////////////////////////////
// Hopefully these are self explanatory //
//////////////////////////////////////////
$l_astPasswdSchemes = array("SLUUSLNN","LSUNLLNU","NNUSLLSN","LNLSUNLU");
$l_iNumPasswds = count($l_astPasswdSchemes);
for ($i=0; $i < $l_iNumPasswds; $i++) {
$l_iSchemeLength = strlen($l_astPasswdSchemes[$i]);
$l_achRandLowercase = array_values(array_rand($l_achLowercase, $l_iNumLowercase));
$l_achRandUppercase = array_values(array_rand($l_achUppercase, $l_iNumUppercase));
$l_aiRandNumbers = array_values(array_rand($l_aiNumbers, $l_iNumNumbers));
$l_achRandSpecialChars = array_values(array_rand($l_achSpecialChars, $l_iNumSpecialChars));
for ($j=0; $j < $l_iSchemeLength; $j++) {
$l_chCurrentOne = $l_astPasswdSchemes[$i]{$j};
switch ($l_chCurrentOne) {
case "L":
$l_astPasswds[$i] .= $l_achLowercase[array_shift($l_achRandLowercase)];
break;
case "U":
$l_astPasswds[$i] .= $l_achUppercase[array_shift($l_achRandUppercase)];
break;
case "N":
$l_astPasswds[$i] .= $l_aiNumbers[array_shift($l_aiRandNumbers)];
break;
case "S":
$l_astPasswds[$i] .= $l_achSpecialChars[array_shift($l_achRandSpecialChars)];
break;
default:
break;
}
}
}
return $l_astPasswds;
}
?>
jpinedo
02-Nov-2003 06:15
02-Nov-2003 06:15
An array of arrays example:
<?php
$banners[0]['imagen']="imagen0.gif";
$banners[0]['url']="www.nosenada.tal";
$banners[1]['imagen']="imagen1.gif";
$banners[1]['url']="www.nose.tal";
$banners[2]['imagen']="imagen2.gif";
$banners[2]['url']="pagina.html";
$banners[3]['imagen']="imagen3.jpg";
$banners[3]['url']="../pagina.php";
$id_banner = array_rand($banners);
echo "Archivo:--".$banners[$id_banner]['imagen']. "<br />\n";
echo "URL:-----".$banners[$id_banner]['url']. "<br />\n";
?>
wazaawazaa600 at msn dot com
16-Oct-2003 04:24
16-Oct-2003 04:24
The function go well ever that you work with a simple array. An array of arrays (also called a table), not works with the function correctly. Example:
<?php
$a=array(array(0,1),array(1,2),array(2,3),array(3,4),array(4,5));
echo $a[0][0];echo"<br>";
echo $a[1][0];echo"<br>";
$b=array_rand($a,2);
echo $b[0][0];echo"<br>"; //This writes nothing
echo $b[1][0];echo"<br>"; //This writes nothing
?>
If you are in this situation, you will need to make your own solution.
asarnoNOSPAM@interbaun DOT com
24-Jun-2003 03:06
24-Jun-2003 03:06
It is correct that using array_rand() with num_req=1 will return an integer and not an array, but why get so complicated with getting just the one value. The K.I.S.S. method would suggest to do it this way:
<?
srand((double)microtime() * 10000000);
$originalArray = array("red", "blue", "green", "brown",
"cyan", "magenta", "purle", "cheezy");
$pickOne = array_rand($originalArray, 1);
$aRandomSelection = $originalArray[$pickOne ];
echo "$aRandomSelection was the random selection made";
?>
You only need to use the foreach if the num_req >=2. In those cases the array_rand() function will return an array of random elements which are a subset of the original array. When num_req = 1, the array_rand() function returns an integer that signifies a randomly picked key of the original array. Hope this clarifies things ... it works for me.
c at aufbix dot org
14-Jun-2003 05:31
14-Jun-2003 05:31
If you use array_rand with num_req=1, it will return an integer, and not an array as it would in all other circumstances. You can bypass that like this:
<?php
$randelts=array_rand($feeds,$num);
for ($j=0;$j<count($randelts);$j++) {
if ($num==1) {$subq[$j]=$feeds[$randelts];}
else {$subq[$j]=$feeds[$randelts[$i]]}
}
?>
Paul Hodel (paul at ue dot com dot br)
18-Apr-2003 05:40
18-Apr-2003 05:40
If you trying to get a randon array just use that... it's easier! And you have no repeats...
<?
srand ((float) microtime() * 10000000);
$input = array ("Neo", "Morpheus", "Trinity", "Cypher", "Tank");
$keys = array_rand ($input, sizeof($input));
while (list($k, $v) = each($keys))
{
echo $new_input = $input[$v];
}
?>
scandar at home dot se
14-Apr-2003 01:58
14-Apr-2003 01:58
Note that the int num_req parameter is the required number of element to randomly select. So if your array has 3 element and num_req=4 then array_rand() will not return anything since it is impossible to select 4 random elements out of an array that only contains 3 elements. Many people think that they will get 3 elements returned but that is of course not the case.
mickoz[at]parodius[dot]com
02-Dec-2002 01:28
02-Dec-2002 01:28
For those of you thinking that it does not work for num_req = 1, it is because it return a variable and not an array. This mainly cause some problem with people using foreach.
The correct way to handle this is explained by that example:
<?php
$some_array = array("blah","bleh","foo","lele");
$nb_value = 1;
srand ((float) microtime() * 10000000);
$rand_keys = array_rand($some_array, $nb_value);
if(!is_array($rand_keys))
{
$rand_keys = array($rand_keys);
}
print_r($rand_keys); // verify here the array of keys
echo "\n<BR>";
?>
// You can then correctly use the foreach, as it require an array to work
// If you use foreach with one element, it won't work.
<?php
$random_array = array();
foreach($rand_keys as $value)
{
array_push($random_array, $some_array[$value]);
}
print_r($random_array);
?>
dboy at jumpstation dot org
23-Jul-2002 10:58
23-Jul-2002 10:58
If you just want to pull one random element from an array, try something like this:
<?php
mt_srand((double) microtime() * 1000000);
$myarray = array("this", "is", "a",
"test", "to", "see",
"if", "I", "can",
"pull", "one", "element",
"from", "an", "array",
"randomly");
$random_index = mt_rand(0, (count($myarray)-1));
?>
Then to test the randomness or what have you try a simple:
<?php
$string = ""; // Just to kill the warning
for ($i=0; $i<count($myarray); $i++) {
$random_index = mt_rand(0, (count($myarray)-1));
$string .= "$myarray[$random_index] ";
}
$string = rtrim($string);
echo ($string);
?>
I've gotten extremely good output from this method and would recommend it if you're just pulling one element.
josh at 3io dot com
15-Jun-2002 07:20
15-Jun-2002 07:20
I modified fake_array_rand to always only return 1 element, and did some benchmarks against calling array_rand with the second parameter as 1. I ran 100 samples for each function for each number of elements and took the average result. While the internal array_rand is faster for a small number of elements, it scales very poorly.
1 elements: 2.0619630813599E-05 sec. for array_rand,8.4352493286133E-05 sec. for fake_array_rand
10 elements: 2.1675825119019E-05 sec. for array_rand,8.427619934082E-05 sec. for fake_array_rand
100 elements: 2.9319524765015E-05 sec. for array_rand,8.4599256515503E-05 sec. for fake_array_rand
1000 elements: 0.0001157283782959 sec. for array_rand,8.5572004318237E-05 sec. for fake_array_rand
10000 elements: 0.0016669762134552 sec. for array_rand,8.5201263427734E-05 sec. for fake_array_rand
100000 elements: 0.015599734783173 sec. for array_rand,8.5580348968506E-05 sec. for fake_array_rand
1000000 elements: 0.18011983394623 sec. for array_rand,8.6690187454224E-05 sec. for fake_array_rand
<?php
function fake_array_rand ($array)
{
$count = count ($array);
# Help keep the number generator random :)
$randval and usleep ("0.$randval");
# Seed the random number generator
# Generate a random number
srand ((double) microtime() * 10000000);
$randval = rand();
# Use the random value to 'pick' an entry from the array
# Count the number of times that the entry is picked
++$index[$randval % $count];
return $array[$randval % $count];
}
?>
uvm at sun dot he dot net
10-Jul-2001 10:09
10-Jul-2001 10:09
If you're just trying to draw a random subset of n elements from an array, it seems more effecient to do something like this:
<?php
function draw_rand_array($array,$draws)
{
$lastIndex = count($array) - 1;
$returnArr = array();
while($draws > 1)
{
$rndIndex = rand(0,$lastIndex);
array_push($returnArr,array_splice($array,$rndIndex,1));
$draws--;
$lastIndex--;
}
return $returnArr;
}
?>
No messing with indexes when you're done... you just have an array with the elements you're looking for in it.