Issue using RecursiveIteratorIterator in a controller

It's a namespace issue. Within your controller, you're in the namespace App\Controllers. The RecursiveIteratorIterator is NOT in that namespace, so you must prefix it with a backslash, or add it as a use statement at the top of the file. That allows PHP to know to look for it in the root namespace, not in the current namespace (App\Controllers).

PHP Code:

$newDataIterator = new \RecursiveIteratorIterator( 
   new \RecursiveArrayIterator(json_decode($dataArray, TRUE)),
   \RecursiveIteratorIterator::SELF_FIRST
); 


or

PHP Code:

<?php namespace App\Controllers;

use RecursiveIteratorIterator;
use RecursiveArrayIterator;

  public function index() {
    $newDataIterator = new RecursiveIteratorIterator( 
        new RecursiveArrayIterator(json_decode($dataArray, TRUE)),
        RecursiveIteratorIterator::SELF_FIRST
    ); 
  }
} 


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