How to remove duplicate values from an array in PHP

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

Use array_unique().

Example:

$array = array(1, 2, 2, 3);
$array = array_unique($array); // Array is now (1, 2, 3)

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 )

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.

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

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 */

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);

$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);

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

This will take care of key associations and serialize the keys for the resulting new 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.

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);

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);

	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

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 )

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

array_keys(array_flip($array));

It's many times faster than array_unique.

We can easily use arrar_unique($array); to remove duplicate elements But the problem in this method is that the index of the elements are not in order, will cause problems if used somewhere else later.

Use

$arr = array_unique($arr);
$arr = array_values($arr);
print_r($arr);

Or

$arr = array_flip($arr);
$arr = array_flip($arr);
$arr = array_values($arr);
print_r($arr);

The first flip , flips the key value pair thus combines the elements with similar key(that was originally the value).

2nd flip to revert all the key value pairs. Finally array_value() sets each value with key starting from 0.

Note: Not to be used in associative array with predefined key value pairs

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

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

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;
}

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<$len;$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
)

<?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 )`

$array = array("a" => "moon", "star", "b" => "moon", "star", "sky");
 
// Deleting the duplicate items
$result = array_unique($array);
print_r($result);

ref : Demo

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>";
}