gistfile1.php

<?php

class ChartA {
  public function getData()
  {
   /** @var $array array */
    $array = $this->getStuffFromStorage();
    
    // Remove null valuse
    
    return $array;
  }
}

class ChartB {
  public function getData()
  {
   /** @var $array array */
    $array = $this->getStuffFromStorage();
    
    // Remove null valuse
    
    return $array;
  }
}

class ChartC {
  public function getData()
  {
   /** @var $array array */
    $array = $this->getStuffFromStorage();
    
    // Remove null valuse
    
    return $array;
  }
}

$chartA = new ChartA();
$chartB = new ChartB();
$chartC = new ChartC();

$chartA->getData();
$chartB->getData();
$chartC->getData();