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array_unique (PHP 4 >= 4.0.1, PHP 5) array_unique -- Removes duplicate values from an array Descriptionarray array_unique ( array array )
array_unique() takes input
array and returns a new array
without duplicate values.
Note that keys are preserved. array_unique() sorts
the values treated as string at first, then will keep the first key
encountered for every value, and ignore all following keys. It does not
mean that the key of the first related value from the unsorted
array will be kept.
Note:
Two elements are considered equal if and only if
(string) $elem1 === (string) $elem2. In words:
when the string representation is the same.
The first element will be used.
Example 1. array_unique() example |
<?php
$input = array("a" => "green", "red", "b" => "green", "blue", "red");
$result = array_unique($input);
print_r($result);
?>
|
The above example will output: |
Array
(
[a] => green
[0] => red
[1] => blue
)
|
|
Example 2. array_unique() and types |
<?php
$input = array(4, "4", "3", 4, 3, "3");
$result = array_unique($input);
var_dump($result);
?>
|
The above example will output: |
array(2) {
[0] => int(4)
[2] => string(1) "3"
}
|
|
User Contributed Notes
array_unique
memandeemail at gmail dot com
15-Apr-2005 03:46
/**
* Removes duplicate keys from an array
*
* @param array $array
* @return array
*/
function array_unique_key($array) {
$result = array();
foreach (array_unique(array_keys($array)) as $tvalue) {
$result[$tvalue] = $array[$tvalue];
}
return $result;
}
Ric
05-Apr-2005 11:44
A very simple way of getting rid of duplicate entries and re-indexing with key starting at 0:
$temp=array_unique($main);
$main=array_values($temp);
trigger at e-mail dot ru
03-Feb-2005 04:53
Just a simple implementation for JavaScript:
function array_unique(thearray)
{
thearray.sort();
//reset($thearray);
newarray = new Array();
for (n=0;n<thearray.length;n++)
{
unique=1;//by default
for(nn=0;nn<newarray.length;nn++)
if (thearray[n] == newarray[nn])
{
unique=0;//already exists
break;
}
if(unique)//dont exists
newarray.push(thearray[n]);
}
return newarray;
}
lucas.bickel AT purplehaze DOT ch
26-Oct-2004 10:39
I quite like the following code for making multidimensional arrays unique:
foreach ($arrAddressList AS $key => $arrAddress) {
$arrAddressList[$key] = serialize($arrAddress);
}
$arrAddressList = array_unique($arrAdressList);
foreach ($arrAddressList AS $key => $strAddress) {
$arrAddressList[$key] = unserialize($strAddress);
}
This gets me a unique array while not minding wether the the original array contains arrays or just strings (or whatever...).
Vary
07-Oct-2004 03:24
This script will unique the array and count the times appearance.
find more information at http://php.scmtv.com/
justin at redwiredesign dot com
14-Sep-2004 08:23
OK, so here's my version that maintains index integrity:
function array_unique($array)
{
$out = array();
// loop through the inbound
foreach ($array as $key=>$value) {
// if the item isn't in the array
if (!in_array($value, $out)) {
// add it to the array
$out[$key] = $value;
}
}
return $out;
}
wernerlistas at terra dot com dot br
16-Jun-2004 10:50
Following the code copies of a little function I've wrote that actually works with multidimensional arrays.
It also resets the array indexes.
<?php
if ( !function_exists( "arrayUnique" ) ){
function arrayUnique ( $rArray ){
$rReturn = array ();
while ( list( $key, $val ) = each ( $rArray ) ){
if ( !in_array( $val, $rReturn ) )
array_push( $rReturn, $val );
}
return $rReturn;
}
}
?>
csaba at alum dot mit dot edu
09-Jun-2004 09:17
The following is an efficient, adaptable implementation of array_unique which always retains the first key having a given value:
<?php
function array_unique2(&$aray) {
$aHash = array();
foreach ($aray as $key => &$val) if (@$aHash[$val]++) unset ($aray[$key]);
}
?>
It is also adaptable to multi dimensional arrays. For example, if your array is a sequence of (multidimensional) points, then in place of @$aHash[$val]++ you could use @$aHash[implode("X",$val)]++
If you want to not have holes in your array, you can do an array_merge($aray) at the end.
Csaba Gabor
patrikG at home dot net
11-Mar-2004 09:05
If you need to have the keys of the duplicates in an array returned, you may find this function useful:
<?php
function unique_events($array){
$count= array_intersect_assoc($array, array_flip( array_count_values($array)));
foreach($array as $key=>$value){
if (in_array($value,$count)){
$return[$value][]=$key;
}
}
return $return;
}
?>
Example:
Input:
Array
(
[0] => 44
[1] => 23
[2] => 23
[3] => 23
[4] => 9
[5] => 9
[6] => 9
[7] => 9
[8] => 9
[9] => 9
[10] => 9
[11] => 9
)
Function returns:
Array
(
[23] => Array
(
[0] => 1
[1] => 2
[2] => 3
)
[9] => Array
(
[0] => 4
[1] => 5
[2] => 6
[3] => 7
[4] => 8
[5] => 9
[6] => 10
[7] => 11
)
)
bitmore.co.kr
19-Feb-2004 05:53
//Modify
Object Unique
<?php
class foo {
var $_name;
var $_age;
function foo($name,$age=NULL) { $this->_name = $name; $this->_age = $age; }
}
function DistinctOn ($obj, $item) {
$out = array();
$list = array();
foreach ($obj as $key=>$so) {
if (!in_array($so->$item, $list)) {
echo "key = $key,so = $so,item = $item,IFlist = ";print_r($list);echo "<br>";
$list[] = $so->$item;$out[$key] = $so;
}
echo "Forlist = ";print_r($list);echo "<br>";
}
return $out;
}
$foo_obj[0] = new foo('tom',20);
$foo_obj[1] = new foo('paul',66);
$foo_obj[2] = new foo('tom',23);
$item = '_name';
$result = DistinctOn ($foo_obj, $item);
while(list($k,$v) = each($result)) {
print "K = ";print_r($k);
print ",V = ";print_r($v);
print "<br>";
}
print "<br><br>";
$item = '_age';
$result = DistinctOn ($foo_obj, $item);
while(list($k,$v) = each($result)) {
print "K = ";print_r($k);
print ",V = ";print_r($v);
print "<br>";
}
?>
matt at remove_mehsmx dot com
17-Feb-2004 06:57
Note that
<?php
array_unique($anyarray);
?>
does not do anything, unlike other array functions such as
<?php
sort($anyarray);
?>
You have to use something like:
<?php
$anyarray = array_unique($anyarray);
?>
14-Jan-2004 07:23
this simple function is similar based on to the function unique_multi_array posted by tru at ascribedata dot com, but will work for objects rather than arrays. use 2d objects. Its eg useful to work with mysql queries since in recent versions, the DISTINCT option in mysql selects will only work when selecting a single (not more) row.
eg.
foo_obj[0]: name: 'tom', age: '20'
foo_obj[1]: name: 'paul', age: '66'
foo_obj[2]: name: 'tom', age: '23'
foo_obj = DistinctOn ($foo_obj, $item) will return
foo_obj[0]: name: 'tom', age: '20'
foo_obj[1]: name: 'paul', age: '66'
<?php
function DistinctOn ($obj, $item) {
$out = array();
$list = array();
foreach ($obj as $key=>$so) {
if (!in_array($so->$item, $list)) {
$list[] = $so->$item;
$out[$key] = $so;
}
}
return $out;
}
?>
tru at ascribedata dot com
16-Oct-2003 06:40
Here's a function to make a multi-dimensional array have only DISTINCT values for a certain "column". It's like using the DISTINCT parameter on a SELECT sql statement.
<?php
function unique_multi_array($array, $sub_key) {
$target = array();
$existing_sub_key_values = array();
foreach ($array as $key=>$sub_array) {
if (!in_array($sub_array[$sub_key], $existing_sub_key_values)) {
$existing_sub_key_values[] = $sub_array[$sub_key];
$target[$key] = $sub_array;
}
}
return $target;
}
?>
kay_rules at yahoo dot com
24-May-2003 04:28
this function will return an array with unique value and proper key increment start from 0.
<?php
function my_array_unique($somearray){
$tmparr = array_unique($somearray);
$i=0;
foreach ($tmparr as $v) {
$newarr[$i] = $v;
$i++;
}
return $newarr;
}
?>
eg:
<?php
$foo_arr[0] ='aa'
$foo_arr[1] ='bb'
$foo_arr[2] ='cc'
$foo_arr[3] ='bb'
$foo_arr[4] ='aa'
$foo_arr[5] ='dd'
?>
normal array_unique will return:
<?php
$foo_arr[0] ='aa';
$foo_arr[1] ='bb';
$foo_arr[2] ='cc';
$foo_arr[3] ='';
$foo_arr[4] ='';
$foo_arr[5] ='dd'
?>
my_array_unique will return:
<?php
$foo_arr[0] ='aa';
$foo_arr[1] ='bb';
$foo_arr[2] ='cc';
$foo_arr[3] ='dd'
?>
martin at lucas-smith dot co dot uk
27-Jan-2003 07:12
To get a list of the duplicated values in an array, array_unique isn't much help. Instead, use array_filter in conjunction with a callback function, as below:
<?php
$checkKeysUniqueComparison = create_function('$value','if ($value > 1) return true;');
$result = array_keys (array_filter (array_count_values($array), $checkKeysUniqueComparison));
?>
These two lines therefore will create $result, an array of duplicated values in the array $array, once each. E.g. the array
$array = array ("a", "b", "a", "b", "x", "y", "z", "x");
gives the result
Array([0] => a [1] => b [2] => x)
juggler at webworkerinfo dot de
10-Jan-2003 07:20
in addition to bisqwit:
in some cases you can simply use serialize instead of recursivemakehash().
<?php
function array_unique2($input) {
$tmp = array();
foreach($input as $a => $b)
$tmp[$a] = serialize($b);
$newinput = array();
foreach(array_unique($tmp) as $a => $b)
$newinput[$a] = $input[$a];
return $newinput;
}
?>
Have fun
Juggler
deigo at swirve dot NOSPAM dot com
23-Sep-2002 12:04
Before I found the mysql distinct I had to make a nicer array from the keys/values that I got from array_unique so.
$groups=array_unique($groups);
$newgroup[0]=reset($groups);
for ($x=1;$x<sizeof($groups);$x++)
{
$newgroup[$x]=next($groups);
}
php at hp-site dot dk
29-Aug-2002 01:15
Try this:
array_flip(array_flip($array));
It gives the same result as the old array_unique()
29-Aug-2002 04:39
<?
$truc = array("l810u00","l810u00","l810q00");
$machin = array_unique($truc);
for($i=0;$i < count($machin) ; $i++){
print $machin[$i]."
";
}
?>
result :
l810u00
This is not strange: $machin (as returned by array unique), contains "l810u00" either in key[0] or key[1] but not both (the key depends on the ersion of PHP), and "l810q00" in key[2].
The returned array has TWO elements so count($machin)==2.
The returned array has a hole in it, and you're not displaying its full content. You could verify it by using this display loop instead:
foreach($machine as $key=>$value){
print '[' . $key . '] => ' . $value . '
";
}
result:
[0] => l810q00
[2] => l810u00
(the first line may display [1] instead of [0] for PHP 4.0.1p3, but you'll get the same order of values and two lines, as expected). When calling array_values() on the result, you're building a new array with the same values in the same order, but with renumbered keys (without holes in numeric keys).
bisqwit at iki dot fi
25-May-2002 10:32
The recursivemakehash() in my previous post contained a flaw. Adding md5() to "return $tab;" fixes it making it now possible to distinguish array(0=>'x') from 'F4DBDF218CDC1683' etc.
bisqwit at iki dot fi
24-May-2002 11:36
array_unique() doesn't return anything useful if your input is an
array containing arrays. This function overcomes the problem.
Any level of recursions is possible here. If the input is a plain
array, the result is compatible with array_unique() result.
<?php
function recursivemakehash($tab)
{
if(!is_array($tab))
return $tab;
$p = '';
foreach($tab as $a => $b)
$p .= sprintf('%08X%08X', crc32($a), crc32(recursivemakehash($b)));
return $p;
}
function array_unique2($input)
{
$dumdum = array();
foreach($input as $a => $b)
$dumdum[$a] = recursivemakehash($b);
$newinput = array();
foreach(array_unique($dumdum) as $a => $b)
$newinput[$a] = $input[$a];
return $newinput;
}
?>
spunk at dasspunk dot NOSPAM dot com
14-Nov-2001 06:52
I needed a way of retaining the original array's keys in the new, unique array. I came up with this. It works for my purposes but may need refinement.
function my_array_unique($somearray)
{
asort($somearray);
reset($somearray);
$currentarrayvar = current($somearray);
foreach ($somearray as $key=>$var)
{
if (next($somearray) != $currentarrayvar)
{
$uniquearray[$key] = $currentarrayvar;
$currentarrayvar = current($somearray);
}
}
reset($uniquearray);
return $uniquearray;
}
ailanto at kafejo dot com
24-Aug-2001 11:04
As in 4.0.3pl1, array_unique() in 4.0.5 returns the *last* key encountered for every value!
eltehaem at N dot O dot S dot P dot A dot M dot free dot poltronic dot net
11-Aug-2001 09:26
>array_unique() will keep the first key encountered
>for every value, and ignore all following keys.
This is true only in PHP 4.0.4pl1, i.e. the code below:
<?php
$temp = Array ('pl', 'pl', 'en', 'en', 'cz', 'de', 'en', 'pl');
print_r($temp);
print_r(array_unique($temp));
?>
Will produce this output:
Array
(
[0] => pl
[1] => pl
[2] => en
[3] => en
[4] => cz
[5] => de
[6] => en
[7] => pl
)
Array
(
[0] => pl
[2] => en
[4] => cz
[5] => de
)
And in PHP 4.0.3pl1 will produce this output:
Array
(
[0] => pl
[1] => pl
[2] => en
[3] => en
[4] => cz
[5] => de
[6] => en
[7] => pl
)
Array
(
[4] => cz
[5] => de
[6] => en
[7] => pl
)
This little function resolves the problem:
<?php
function my_array_unique(&$old){
$new = array();
foreach($old as $key => $value){
if(!in_array($value, $new)) $new[$key] = $value;
}
return $new;
}
?>
az at top-webdesign dot de
10-Jul-2001 03:00
Attention!
If you use array_unique be aware of data-types! (I spent hours of debugging because of that ...).
For example, if you've got an array containing a '3' as number and another '3' as string it won't be eliminated by array_unique.
An Example where this can happen, without really thinking about it:
I've got an article-list with product-numbers where the third and fourth digit is the code for the producer. So I read in the file an process it line by line and put each producer-code into an array:
------------------------------
<?php
$i=0;
while($line = fgets($csv, 10000) {
$data = explode(";", $line);
$producer_id[$i] = trim(substr($data[0], 2, 2));
if(trim(substr($data[0], 2, 2)) == 40) {
$producer_id[$j] = '30';
}
$i++;
}
$producer_ids = array_values(array_unique($producer_id));
?>
-------------------------------
Result is to have all producer-ID's in an array without dupes.
az at top-webdesign dot de
10-Jul-2001 02:38
@lefeuvrenicolas
Use the above mentioned combination with "array_values" - then it works.
So do it like this:
--------------------
<?php
$truc = array("l810u00","l810u00","l810q00");
$machin = array_values(array_unique($truc));
for($i=0;$i < count($machin) ; $i++){
echo $machin[$i]."\n";
}
?>
--------------------
But it is strange anyway ...
mads dot rebsdorf at am-vision dot dk
07-May-2001 07:55
To unique an array in newer versions of php - i've found this snippet useful:
<?php
$new = array();
for($i=0;$i<count($old);++$i){
if(in_array($old[$i], $new) != "true"){
$new[] = $old[$i];
}
}
?>
/mads
rein at velt dot net
21-Apr-2001 02:44
Following code copies unique values from MyArray to TempArray.
Then copies non-empty elements from TempArray to UniqueArray.
Not the most elegant solution, but it works.
<?php
$TempArray = array_unique($MyArray);
while (list($index,$data)=each($TempArray)) {
if (isempty($data)) {
$UniqueArray[$index]=$data;
}
}
?>
sneze at yahoo dot com
10-Feb-2001 11:47
$users = array_unique($online_users);
foreach($users as $value){
echo $value;
}
saved my day
burno at 33-24-36 dot com
10-Nov-2000 05:28
Or just do a usort($myArray,"return -1"); after the usage of array_unique
matthew_dean at hotmail dot com
26-Oct-2000 09:04
Re: Useful comments from jllamas@bal.com.mx
If you are using a numerically indexed array and you want to make it unique but *with* consecutive indices, you can use array_values(array_unique($myArray));
jllamas at bal dot com dot mx
25-Sep-2000 11:25
It seems that array_unique creates an exact copy of the original array and then elimitates duplicate values. It does NOT change the "internal references" of the array. For example:
<?php
$test_alfa = array();
$test_alfa[0] = "aa";
$test_alfa[1] = "aa";
$test_alfa[2] = "aa";
$test_alfa[3] = "bb";
$test_alfa[4] = "aa";
$test_alfa[5] = "bb";
$test_alfa[6] = "cc";
$test_alfa[7] = "bb";
$test_beta= array_unique($test_alfa);
$numValues = count($test_beta);
for ($i = 0 ; $i <= 7 ; $i++)
echo("test_beta[$i] = $test_beta[$i] <br>");
echo ("Number of elements in test_beta = $numValues ");
?>
will give you the following output:
test_beta[0] =
test_beta[1] = aa
test_beta[2] =
test_beta[3] =
test_beta[4] =
test_beta[5] = bb
test_beta[6] = cc
test_beta[7] =
Number of elements in test_beta = 3
The point is that you won't get the output you'd expect if you think that the values of the non duplicate elements are located in the first three array locations.
$numValues = count($test_beta);
for ($i=0;$i<=$numValues; $i++)
echo("test_beta[$i] = $test_beta[$i] <br>");
echo ("Number of elements in test_beta = $numValues ");
will give you:
test_beta[0] =
test_beta[1] = aa
test_beta[2] =
Number of elements in test_beta = 3
Hope that saves u some debugging time!
sterba at locksley-west dot com
05-Sep-2000 02:30
Maybe this will come handy for PHP3 users:
<?php
for ($a = 0; $a < $arraylength; $a++){
if (($a > 0)&&($array[$a] <> $array[$a-1]))
$uniquearray[$a] = $array[$a];
$a++;
}
?>
You can even skip the $a>0 test, I believe... not bulletproof, but much shorter.
moose at ucdavis dot edu
15-Aug-2000 04:08
Here's a little function I wrote that's similar to array_unique, for PHP3 users. It actually removes duplicated elements, but only works for 1 dimensional arrays. It also doesn't return a value, it changes the input array:
<?php
function array_unique(&$thearray)
{sort($thearray);
reset($thearray);
$newarray = array();
$i = 0;
$element = current($thearray);
for ($n=0;$n<sizeof($thearray);$n++)
{if (next($thearray) != $element)
{$newarray[$i] = $element;
$element = current($thearray);
$i++;
}
}
$thearray = $newarray;
}
?>
| |
array_uintersect