Prevent repeats using array_rand PHP

Question

I have a list of images and I have a wordpress loop.

I use the randompics() function to generate a random image to use as a background to the prreview link. However, Im finding that Im generating repeat images here and there and it doesnt look great.

I would like to find a way to ensure that I dont have the same image more than once. There are only ever 10 iterations of the loop on any one page.

Here is my function.

function randompics() {
  $arrayName = array(
    get_template_directory_uri().'/images/jobs_large/1.jpg',
    get_template_directory_uri().'/images/jobs_large/2.jpg',
    get_template_directory_uri().'/images/jobs_large/3.jpg',
    get_template_directory_uri().'/images/jobs_large/4.jpg',
    get_template_directory_uri().'/images/jobs_large/5.jpg',
    get_template_directory_uri().'/images/jobs_large/6.jpg',
    get_template_directory_uri().'/images/jobs_large/7.jpg',
    get_template_directory_uri().'/images/jobs_large/8.jpg',
    get_template_directory_uri().'/images/jobs_large/9.jpg',
    get_template_directory_uri().'/images/jobs_large/11.jpg',
    get_template_directory_uri().'/images/jobs_large/12.jpg',    
    //list goes up to 25 images
  );
 echo $arrayName[array_rand($arrayName)];
}

Heres my loop

<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>

  <div class="item-container">
    <?php randompics(); ?>
  </div>

<?php endwhile; else : endif;?>

Thanks in advance.

Why not use an other variable to serve as an index that increments in every iteration, an then randompics($index); without using array_rand() I mean? — Hamza Abdaoui
– Hamza Abdaoui, Commented Jan 26, 2018 at 16:16
you can use a "temp memory". If this generation is user-based you can use the $_SESSION variable to store the images already displayed, otherwise you can choose a file-based temp memory to store. — Oscar Zarrus
– Oscar Zarrus, Commented Jan 26, 2018 at 16:16
Create one array of images, shuffle it, then pick from the array in order… — deceze
– deceze ♦, Commented Jan 26, 2018 at 16:26

Stratadox · Accepted Answer · 2018-01-26 16:28:39Z

I suppose the easiest way is to use static variables:

function randompics() {
  static $arrayName = null;
  if (is_null($arrayNme)) {
    $arrayName = array(
      get_template_directory_uri().'/images/jobs_large/1.jpg',
      get_template_directory_uri().'/images/jobs_large/2.jpg',   
      //list goes up to 25 images
    );
    shuffle($arrayName);
  }
  static $index = 0;
  echo $arrayName[$index++];
}

This does share data between function calls, however, which is generally discouraged. A better solution (at least IMHO) would be to use an ImageRandomiser class and have an object of that class keep track of duplicates.

Use, for instance:

class ImageRandomiser
{
  private $images;
  private $index;

  public function __construct(string ...$imageUris)
  {
    $this->index = 0;
    $this->images = $imageUris;
    shuffle($this->images);
  }

  public static function fromDefaults() : self
  {
    return new static(
      get_template_directory_uri().'/images/jobs_large/1.jpg',
      get_template_directory_uri().'/images/jobs_large/2.jpg',
      // ...
    );
  }

  public function imageUri() : string
  {
    $this->index++;
    if ($this->index >= count($this->images)) {
      $this->index = 0;
    }
    return $this->images[$this->index];
  }
}

The loop:

<?php 
$random = ImageRandomiser::fromDefaults();
if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>

  <div class="item-container">
    <?php $random->imageUri(); ?>
  </div>

<?php endwhile; else : endif; ?>

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