How to remove duplicate values from array in foreach loop?

Question

I want to remove duplicate values from array. I know to use array_unique(array) function but faced problem in foreach loop. This is not a duplicate question because I have read several questions regarding this and most of them force to use array_unique(array) function but I have no idea to use it in foreach loop. Here is my php function.

$images = scandir($dir);
$listImages=array();
foreach($images as $image){
    $listImages=$image;
    echo substr($listImages, 0, -25) ."<br>"; //remove last 25 chracters
}

How to do this?

yes you can use array_unique after ending your foreach loop. — Ashok Chandrapal, Oct 14 '16 at 12:39
`Use array_unique()` ?? something like `array_unique($images)` — devpro, Oct 14 '16 at 12:39
Your code is nothing to do with what you say. If you want to delete duplicates from an array in an alternative way please use a double iteration classic pattern — manuelbcd, Oct 14 '16 at 12:42
Looking at your code, `$images` should already contain a unique array of filenames (no OS allows for duplicate filenames. The closest you can come is *nix case-sensative filenames, e.g. `ab.txt` != `AB.txt`, but is still a valid unique filename). Could you explain what it is you are trying to achieve? — Richard Parnaby-King, Oct 14 '16 at 13:11

score 8 · Accepted Answer · answered Oct 17 '16 at 06:40

It is very complicated to remove duplicate values from array within foreach loop. Simply you can push all elements to one array and then remove the duplicates and then get values as you need. Try with following code.

   $listImages=array();
   $images = scandir($dir);

   foreach($images as $image){
       $editedImage = substr($image, 0, -25);
       array_push($listImages, $editedImage);
   } 

   $filteredList = array_unique($listImages);

   foreach($filteredList as $oneitem){
       echo $oneitem;
   }

mister martin · Answer 2 · 2016-10-14T12:55:07.957

1

The example you provided could be modified as follows:

$images = scandir($dir);
$listImages=array();
foreach($images as $image) {
    if (!in_array($image, $listImages)) {
        $listImages[] = $image;
    }
    echo substr($image, 0, -25) ."<br>"; //remove last 25 chracters
}

Now $listImages will contain no duplicates, and it will echo every image (including duplicates).

edited Oct 14 '16 at 12:55

answered Oct 14 '16 at 12:40

mister martin

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@ mister martin, it will be optimized if will use `array_unique($listImages)` after loop end. for now you did check everytime in loop. – Ashok Chandrapal Oct 14 '16 at 12:43
why to down vote... if answer is correct and different from you @mister martin – Veshraj Joshi Oct 14 '16 at 12:50
I want to print each and every value within the foreach loop. So cant use `array_unique($listImages)` after loop end – Bandara Oct 14 '16 at 12:52

score 1 · Answer 3 · answered Oct 14 '16 at 13:07

Based on @mistermartins answer:

$images = scandir($dir);
$listImages=array();
foreach($images as $image) {
    //if already echo'd continue to next iteration
    if (in_array($image, $listImages)) {
        continue;
    }
    //else, add image to array and echo.
    $listImages[] = $image;
    echo substr($image, 0, -25) ."<br>"; //remove last 25 chracters
}

score 0 · Answer 4 · answered Oct 14 '16 at 13:11

It should be faster to use hashmaps:

$images = scandir($dir);
$listImages = array();
foreach($images as $image) {
    if (!isset($listImages[$image])) {
        $listImages[$image] = true;
        echo substr($image, 0, -25) ."<br>"; //remove last 25 chracters
    }
}

score 0 · Answer 5 · answered Oct 14 '16 at 13:25

I'm not sure if I have understood you completely. Subsequent approach worked for me in order to remove duplicate indizes from array using a foreeach loop.

$list = array("hans", "peter", "hans", "lara", "peter", "lara", "lara");
sort($list);
foreach ($list as $k => $v) {
     if (isset($check)) {
        if ($check === $v) {
            unset($list[$k]);
        }
     }
     $check = $v;
}

$noDuplicate = array_values($list);

print_r($noDuplicate);

gives following result:

Array ( [0] => hans [1] => lara [2] => peter )

How to remove duplicate values from array in foreach loop?

5 Answers5