[php] How to remove duplicate values from an array in PHP

How can I remove duplicate values from an array in PHP?

function arrayUnique($myArray)
{
    $newArray = Array();
    if (is_array($myArray))
    {
        foreach($myArray as $key=>$val)
        {
            if (is_array($val))
            {
                $val2 = arrayUnique($val);
            }
            else
            {
                $val2 = $val;
                $newArray=array_unique($myArray);
                $newArray=deleteEmpty($newArray);
                break;
            }
            if (!empty($val2))
            {
                $newArray[$key] = $val2;
            }
        }
    }
    return ($newArray);
}

function deleteEmpty($myArray)
{
    $retArray= Array();
    foreach($myArray as $key=>$val)
    {
        if (($key<>"") && ($val<>""))
        {
            $retArray[$key] = $val;
        }
    }
    return $retArray;
}

explode(",", implode(",", array_unique(explode(",", $YOUR_ARRAY))));

This will take care of key associations and serialize the keys for the resulting new array :-)

That's a great way to do it. Might want to make sure its output is back an array again. Now you're only showing the last unique value.

Try this:

$arrDuplicate = array ("","",1,3,"",5);

foreach (array_unique($arrDuplicate) as $v){
  if($v != "") { $arrRemoved[] = $v; }
}
print_r ($arrRemoved);

try this short & sweet code -

$array = array (1,4,2,1,7,4,9,7,5,9);
$unique = array();

foreach($array as $v){
  isset($k[$v]) || ($k[$v]=1) && $unique[] = $v;
  }

var_dump($unique);

Output -

array(6) {
  [0]=>
  int(1)
  [1]=>
  int(4)
  [2]=>
  int(2)
  [3]=>
  int(7)
  [4]=>
  int(9)
  [5]=>
  int(5)
}

The array_unique function is just one of the really useful native functions from PHP for dealing with arrays. I recently wrote a piece on them and the spread operator to modifying and manipulating PHP arrays:

https://wp-helpers.com/2021/02/27/php-arrays-functions-and-spread-operator-in-wp-context/

There can be multiple ways to do these, which are as follows

//first method
$filter = array_map("unserialize", array_unique(array_map("serialize", $arr)));

//second method
$array = array_unique($arr, SORT_REGULAR);

I have done this without using any function.

$arr = array("1", "2", "3", "4", "5", "4", "2", "1");

$len = count($arr);
for ($i = 0; $i < $len; $i++) {
  $temp = $arr[$i];
  $j = $i;
  for ($k = 0; $k < $len; $k++) {
    if ($k != $j) {
      if ($temp == $arr[$k]) {
        echo $temp."<br>";
        $arr[$k]=" ";
      }
    }
  }
}

for ($i = 0; $i < $len; $i++) {
  echo $arr[$i] . " <br><br>";
}

<?php
$a=array("1"=>"302","2"=>"302","3"=>"276","4"=>"301","5"=>"302");
print_r(array_values(array_unique($a)));
?>//`output -> Array ( [0] => 302 [1] => 276 [2] => 301 )`

The array_unique function is just one of the really useful native functions from PHP for dealing with arrays. I recently wrote a piece on them and the spread operator to modifying and manipulating PHP arrays:

https://wp-helpers.com/2021/02/27/php-arrays-functions-and-spread-operator-in-wp-context/

It can be done through function I made three function duplicate returns the values which are duplicate in array.

Second function single return only those values which are single mean not repeated in array and third and full function return all values but not duplicated if any value is duplicated it convert it to single;

function duplicate($arr) {
    $duplicate;
    $count = array_count_values($arr);
    foreach($arr as $key => $value) {
        if ($count[$value] > 1) {
            $duplicate[$value] = $value;
        }
    }
    return $duplicate;
}
function single($arr) {
    $single;
    $count = array_count_values($arr);
    foreach($arr as $key => $value) {
        if ($count[$value] == 1) {
            $single[$value] = $value;
        }
    }
    return $single;
}
function full($arr, $arry) {
    $full = $arr + $arry;
    sort($full);
    return $full;
}

<?php
$a=array("1"=>"302","2"=>"302","3"=>"276","4"=>"301","5"=>"302");
print_r(array_values(array_unique($a)));
?>//`output -> Array ( [0] => 302 [1] => 276 [2] => 301 )`

    if (@!in_array($classified->category,$arr)){        
                                    $arr[] = $classified->category;
                                 ?>

            <?php } endwhile; wp_reset_query(); ?>

first time check value in array and found same value ignore it

$a = array(1, 2, 3, 4); 
$b = array(1, 6, 5, 2, 9); 
$c = array_merge($a, $b);
$unique = array_keys(array_flip($c));
print_r($unique);

An alternative for array_unique() function..

Using Brute force algorithm

//[1] This our array with duplicated items
$matches = ["jorge","melvin","chelsy","melvin","jorge","smith"];
//[2] Container for the new array without any duplicated items
$arr = [];
//[3] get the length of the duplicated array and set it to the var len to be use for for loop
$len = count($matches);
//[4] If matches array key($i) current loop Iteration is not available in
//[4] the array $arr then push the current iteration key value of the matches[$i]
//[4] to the array arr.
for($i=0;$i
if(array_search($matches[$i], $arr) === false){
array_push($arr,$matches[$i]);
}
}
//print the array $arr.
print_r($arr);
//Result: Array
(
[0] => jorge
[1] => melvin
[2] => chelsy
[3] => smith
)

    if (@!in_array($classified->category,$arr)){        
                                    $arr[] = $classified->category;
                                 ?>

            <?php } endwhile; wp_reset_query(); ?>

first time check value in array and found same value ignore it

<?php
$arr1 = [1,1,2,3,4,5,6,3,1,3,5,3,20];    
print_r(arr_unique($arr1));


function arr_unique($arr) {
  sort($arr);
  $curr = $arr[0];
  $uni_arr[] = $arr[0];
  for($i=0; $i<count($arr);$i++){
      if($curr != $arr[$i]) {
        $uni_arr[] = $arr[$i];
        $curr = $arr[$i];
      }
  }
  return $uni_arr;
}

Here I've created a second empty array and used for loop with the first array which is having duplicates. It will run as many time as the count of the first array. Then compared with the position of the array with the first array and matched that it has this item already or not by using in_array. If not then it'll add that item to second array with array_push.

$a = array(1,2,3,1,3,4,5);
$count = count($a);
$b = [];
for($i=0; $i<$count; $i++){
    if(!in_array($a[$i], $b)){
        array_push($b, $a[$i]);
    }
}
print_r ($b);

<?php
$arr1 = [1,1,2,3,4,5,6,3,1,3,5,3,20];    
print_r(arr_unique($arr1));


function arr_unique($arr) {
  sort($arr);
  $curr = $arr[0];
  $uni_arr[] = $arr[0];
  for($i=0; $i<count($arr);$i++){
      if($curr != $arr[$i]) {
        $uni_arr[] = $arr[$i];
        $curr = $arr[$i];
      }
  }
  return $uni_arr;
}

$a = array(1, 2, 3, 4); 
$b = array(1, 6, 5, 2, 9); 
$c = array_merge($a, $b);
$unique = array_keys(array_flip($c));
print_r($unique);

function arrayUnique($myArray)
{
    $newArray = Array();
    if (is_array($myArray))
    {
        foreach($myArray as $key=>$val)
        {
            if (is_array($val))
            {
                $val2 = arrayUnique($val);
            }
            else
            {
                $val2 = $val;
                $newArray=array_unique($myArray);
                $newArray=deleteEmpty($newArray);
                break;
            }
            if (!empty($val2))
            {
                $newArray[$key] = $val2;
            }
        }
    }
    return ($newArray);
}

function deleteEmpty($myArray)
{
    $retArray= Array();
    foreach($myArray as $key=>$val)
    {
        if (($key<>"") && ($val<>""))
        {
            $retArray[$key] = $val;
        }
    }
    return $retArray;
}

$result = array();
foreach ($array as $key => $value){
  if(!in_array($value, $result))
    $result[$key]=$value;
}

$arrDuplicate = array ("","",1,3,"",5);
 foreach(array_unique($arrDuplicate) as $v){
  if($v != "" ){$arrRemoved = $v;  }}
print_r($arrRemoved);

Here I've created a second empty array and used for loop with the first array which is having duplicates. It will run as many time as the count of the first array. Then compared with the position of the array with the first array and matched that it has this item already or not by using in_array. If not then it'll add that item to second array with array_push.

$a = array(1,2,3,1,3,4,5);
$count = count($a);
$b = [];
for($i=0; $i<$count; $i++){
    if(!in_array($a[$i], $b)){
        array_push($b, $a[$i]);
    }
}
print_r ($b);

We can create such type of array to use this last value will be updated into column or key value and we will get unique value from the array...

$array = array (1,3,4,2,1,7,4,9,7,5,9);
    $data=array();
    foreach($array as $value ){

        $data[$value]= $value;

    }

    array_keys($data);
    OR
    array_values($data);

Remove duplicate values from an associative array in PHP.

$arrDup = Array ('0' => 'aaa-aaa' , 'SKU' => 'aaa-aaa' , '1' => '12/1/1' , 'date' => '12/1/1' , '2' => '1.15' , 'cost' => '1.15' );

foreach($arrDup as $k =>  $v){
  if(!( isset ($hold[$v])))
      $hold[$v]=1;
  else
      unset($arrDup[$k]);
}

Array ( [0] => aaa-aaa [1] => 12/1/1 [2] => 1.15 )

We can create such type of array to use this last value will be updated into column or key value and we will get unique value from the array...

$array = array (1,3,4,2,1,7,4,9,7,5,9);
    $data=array();
    foreach($array as $value ){

        $data[$value]= $value;

    }

    array_keys($data);
    OR
    array_values($data);

$array = array("a" => "moon", "star", "b" => "moon", "star", "sky");

// Deleting the duplicate items
$result = array_unique($array);
print_r($result);

ref : Demo

Use array_values(array_unique($array));

array_unique: for unique array array_values: for reindexing

$result = array();
foreach ($array as $key => $value){
  if(!in_array($value, $result))
    $result[$key]=$value;
}

Depending on the size of your array, I have found

$array = array_values( array_flip( array_flip( $array ) ) );

can be faster than array_unique.

There can be multiple ways to do these, which are as follows

//first method
$filter = array_map("unserialize", array_unique(array_map("serialize", $arr)));

//second method
$array = array_unique($arr, SORT_REGULAR);

The only thing which worked for me is:

$array = array_unique($array, SORT_REGULAR);

Edit : SORT_REGULAR keeps the same order of the original array.

Depending on the size of your array, I have found

$array = array_values( array_flip( array_flip( $array ) ) );

can be faster than array_unique.

It can be done through function I made three function duplicate returns the values which are duplicate in array.

Second function single return only those values which are single mean not repeated in array and third and full function return all values but not duplicated if any value is duplicated it convert it to single;

function duplicate($arr) {
    $duplicate;
    $count = array_count_values($arr);
    foreach($arr as $key => $value) {
        if ($count[$value] > 1) {
            $duplicate[$value] = $value;
        }
    }
    return $duplicate;
}
function single($arr) {
    $single;
    $count = array_count_values($arr);
    foreach($arr as $key => $value) {
        if ($count[$value] == 1) {
            $single[$value] = $value;
        }
    }
    return $single;
}
function full($arr, $arry) {
    $full = $arr + $arry;
    sort($full);
    return $full;
}

I have done this without using any function.

$arr = array("1", "2", "3", "4", "5", "4", "2", "1");

$len = count($arr);
for ($i = 0; $i < $len; $i++) {
  $temp = $arr[$i];
  $j = $i;
  for ($k = 0; $k < $len; $k++) {
    if ($k != $j) {
      if ($temp == $arr[$k]) {
        echo $temp."<br>";
        $arr[$k]=" ";
      }
    }
  }
}

for ($i = 0; $i < $len; $i++) {
  echo $arr[$i] . " <br><br>";
}

sometimes array_unique() is not the way, if you want get unique AND duplicated items...

$unique=array("","A1","","A2","","A1","");
$duplicated=array();

foreach($unique as $k=>$v) {

if( ($kt=array_search($v,$unique))!==false and $k!=$kt )
 { unset($unique[$kt]);  $duplicated[]=$v; }

}

sort($unique); // optional
sort($duplicated); // optional

results on

array ( 0 => '', 1 => 'A1', 2 => 'A2', ) /* $unique */

array ( 0 => '', 1 => '', 2 => '', 3 => 'A1', ) /* $duplicated */

If you concern in performance and have simple array, use:

array_keys(array_flip($array));

It's many times faster than array_unique.

Remove duplicate values from an associative array in PHP.

$arrDup = Array ('0' => 'aaa-aaa' , 'SKU' => 'aaa-aaa' , '1' => '12/1/1' , 'date' => '12/1/1' , '2' => '1.15' , 'cost' => '1.15' );

foreach($arrDup as $k =>  $v){
  if(!( isset ($hold[$v])))
      $hold[$v]=1;
  else
      unset($arrDup[$k]);
}

Array ( [0] => aaa-aaa [1] => 12/1/1 [2] => 1.15 )

//Find duplicates 

$arr = array( 
    'unique', 
    'duplicate', 
    'distinct', 
    'justone', 
    'three3', 
    'duplicate', 
    'three3', 
    'three3', 
    'onlyone' 
);

$unique = array_unique($arr); 
$dupes = array_diff_key( $arr, $unique ); 
    // array( 5=>'duplicate', 6=>'three3' 7=>'three3' )

// count duplicates

array_count_values($dupes); // array( 'duplicate'=>1, 'three3'=>2 )

That's a great way to do it. Might want to make sure its output is back an array again. Now you're only showing the last unique value.

Try this:

$arrDuplicate = array ("","",1,3,"",5);

foreach (array_unique($arrDuplicate) as $v){
  if($v != "") { $arrRemoved[] = $v; }
}
print_r ($arrRemoved);

try this short & sweet code -

$array = array (1,4,2,1,7,4,9,7,5,9);
$unique = array();

foreach($array as $v){
  isset($k[$v]) || ($k[$v]=1) && $unique[] = $v;
  }

var_dump($unique);

Output -

array(6) {
  [0]=>
  int(1)
  [1]=>
  int(4)
  [2]=>
  int(2)
  [3]=>
  int(7)
  [4]=>
  int(9)
  [5]=>
  int(5)
}

sometimes array_unique() is not the way, if you want get unique AND duplicated items...

$unique=array("","A1","","A2","","A1","");
$duplicated=array();

foreach($unique as $k=>$v) {

if( ($kt=array_search($v,$unique))!==false and $k!=$kt )
 { unset($unique[$kt]);  $duplicated[]=$v; }

}

sort($unique); // optional
sort($duplicated); // optional

results on

array ( 0 => '', 1 => 'A1', 2 => 'A2', ) /* $unique */

array ( 0 => '', 1 => '', 2 => '', 3 => 'A1', ) /* $duplicated */

explode(",", implode(",", array_unique(explode(",", $YOUR_ARRAY))));

This will take care of key associations and serialize the keys for the resulting new array :-)

Use array_values(array_unique($array));

array_unique: for unique array array_values: for reindexing

//Find duplicates 

$arr = array( 
    'unique', 
    'duplicate', 
    'distinct', 
    'justone', 
    'three3', 
    'duplicate', 
    'three3', 
    'three3', 
    'onlyone' 
);

$unique = array_unique($arr); 
$dupes = array_diff_key( $arr, $unique ); 
    // array( 5=>'duplicate', 6=>'three3' 7=>'three3' )

// count duplicates

array_count_values($dupes); // array( 'duplicate'=>1, 'three3'=>2 )

$arrDuplicate = array ("","",1,3,"",5);
 foreach(array_unique($arrDuplicate) as $v){
  if($v != "" ){$arrRemoved = $v;  }}
print_r($arrRemoved);

An alternative for array_unique() function..

Using Brute force algorithm

//[1] This our array with duplicated items
$matches = ["jorge","melvin","chelsy","melvin","jorge","smith"];
//[2] Container for the new array without any duplicated items
$arr = [];
//[3] get the length of the duplicated array and set it to the var len to be use for for loop
$len = count($matches);
//[4] If matches array key($i) current loop Iteration is not available in
//[4] the array $arr then push the current iteration key value of the matches[$i]
//[4] to the array arr.
for($i=0;$i
if(array_search($matches[$i], $arr) === false){
array_push($arr,$matches[$i]);
}
}
//print the array $arr.
print_r($arr);
//Result: Array
(
[0] => jorge
[1] => melvin
[2] => chelsy
[3] => smith
)

The only thing which worked for me is:

$array = array_unique($array, SORT_REGULAR);

Edit : SORT_REGULAR keeps the same order of the original array.

$array = array("a" => "moon", "star", "b" => "moon", "star", "sky");

// Deleting the duplicate items
$result = array_unique($array);
print_r($result);

ref : Demo