Remove duplicates – array_unique()

I was able to answer my question thanks to : https://wpquestions.com/Remove_duplicates_from_ACF_query/12685

<?php
    $posts = get_posts(array(
    'numberposts' => -1,
    'post_type' => 'page',
    'orderby' => 'meta_value',
    'order' => 'ASC',
    ));
if($posts)
    { /* FIRST, get all the post data */
        foreach($posts as $post)
    { /* SECOND, one-by-one, add each data row for the specific field into an array */
        $io_names[] = get_field('io_name');
    } /* THIRD, run through the array and remove all duplicates */
        $io_names = array_unique($io_names);
        foreach($io_names as $io_name)
            { /* FINALLY, display the data on the page  */
            echo '<p><a href="#">' . $io_name . '</a></p>';
            }   
    }
?>