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
– Ashok Chandrapal, Commented Oct 14, 2016 at 12:39
Use array_unique() ?? something like array_unique($images) — devpro
– devpro, Commented Oct 14, 2016 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
– manuelbcd, Commented Oct 14, 2016 at 12:42

isuru · Accepted Answer · 2016-10-17 06:40:51Z

8

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;
   }

answered Oct 17, 2016 at 6:40

isuru

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Comments

mister martin · Accepted Answer · 2016-10-14 12:55:07Z

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, 2016 at 12:55

answered Oct 14, 2016 at 12:40

mister martin

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3 Comments

Ashok Chandrapal Over a year ago

@ mister martin, it will be optimized if will use array_unique($listImages) after loop end. for now you did check everytime in loop.

Veshraj Joshi Over a year ago

why to down vote... if answer is correct and different from you @mister martin

Bandara Over a year ago

I want to print each and every value within the foreach loop. So cant use array_unique($listImages) after loop end

Richard Parnaby-King · Accepted Answer · 2016-10-14 13:07:40Z

1

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
}

answered Oct 14, 2016 at 13:07

Richard Parnaby-King

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Comments

danopz · Accepted Answer · 2016-10-14 13:11:15Z

0

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
    }
}

answered Oct 14, 2016 at 13:11

danopz

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Comments

Friedrich Siever · Accepted Answer · 2016-10-14 13:25:41Z

0

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 )

answered Oct 14, 2016 at 13:25

Friedrich Siever

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