How to remove duplicate values from an array in PHP

Question

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

Jeremy_Ruten_813 · Answer

Use array_unique().

Example:

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

user_9067214 · Answer

$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);

user_8473036 · Answer

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);

user_16402248 · Answer

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

user_19637635 · Answer

This example is just an alternative.

user_2470765 · Answer

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

array_keys(array_flip($array));

It's many times faster than array_unique.

user_10742699 · Answer

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);

user_9606216 · Answer

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
)

user_13643802 · Answer

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

user_288286 · Answer

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."
";
        $arr[$k]=" ";
      }
    }
  }
}

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

";
}

user_3996624 · Answer

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

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

ref : Demo

How to remove duplicate values from an array in PHP

27 Answers