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Here’s the improved answer

//The Function
    function in_array_r($needle, $haystack, $strict = false) {
        foreach ($haystack as $item) {
            if (($strict ? $item === $needle : $item == $needle) || (is_array($item) && in_array_r($needle, $item, $strict))) {
                return true;
                $found = 'yes';
            }
        }
        $found = 'no';
        return false;
    }

//The Function in use
        //Set the result as a var so you can check it.
  $found = in_array_r($search_pre_order_date,$dates_array) ? 'found' : 'not found';
  
        //If the result is equal to something do something...
        if ($found == 'found') {
    echo 'Yes this item is in the array';
  }elseif ($found == 'not found') {
                echo 'Nope not in the array';
  }

Dynamic Featured Image

add_action( 'admin_head', 'remove_my_meta_boxen' );
function remove_my_meta_boxen() {
    remove_meta_box( 'postimagediv', 'countries', 'side' );
    add_meta_box('postimagediv', __('Country Flag'), 'post_thumbnail_meta_box', 'countries', 'side', 'high');
}

The post type in this example is countries

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This example uses Font Awesome. Don’t forget to include Font Awesome lib in your functions.php

jQuery(document).ready(function($) {

  // Test
    console.log( "ready!" );
  

});