simple general PHP lazy loader

example1.php

<?php

$chart = $chartMapper->getChartById($chartId); 
$user = $chart->getUser(); 
$client = $chart->getClient(); 
$trend = $chart->getTrend();

?>

example2.php

<?php

$chart = $chartMapper->getChartById($chartId); 
$user = $userMapper->getUserByChartId($chartId); 
$client = $clientMapper->getClientByChartId($chartId); 
$trend = $trendMapper->getTrendByChartId($chartId);

?>

exampleChart.php

<?php

class Chart{ 
    private $id; 
     private $name; 
     private $lazyLoadedUser; 
 
     public function __construct($id, $name){ 
         $this->id = $id; 
         $this->name = $name; 
     } 
 
     public function setName($name){ 
         return $this->name = $name; 
     }        
 
     public function getName(){ 
         return $this->name; 
     } 
 
     public function setUser($userOrProvider){ 
         $this->lazyLoadedUser = new LazyLoader($userOrProvider); 
     } 
 
     public function getUser(){ 
         return call_user_func($this->lazyLoadedUser); 
     }  
 } 

?>

exampleChartMapper.php

<?php

class ChartMapper{ 
 
     public function getChart($chartId){ 
         ... sql sql sql ... 
 
        $chart = new Chart(...);
        $chart->setUser( 
             function() use ($chartId, $userMapper){ 
                 return $userMapper->getUserByChartId($chartId); 
             } 
        ); 
        return $chart; 
    }  
}

?>

LazyLoader.php

<?php

class LazyLoader{ 
     private $providerOrValue; 
     private $evaluated = false; 
      
     public function __construct($providerOrValue) { 
         $this->providerOrValue = $providerOrValue; 
     } 
      
     public function __invoke(){ 
         if (!$this->evaluated){ 
             if (is_callable($this->providerOrValue)) 
                 $this->providerOrValue = call_user_func ($this->providerOrValue); 
             $this->evaluated = true; 
         } 
         return $this->providerOrValue;            
     }       
 }
  
?>

oneLiner.php

<?php

$otherUsersOnSameClient = $chart->getClient()->getAllUsers();

?>