PHP遍歴配列付与方式比較

header("Content-type:text/html;charset=utf-8"); 
 $arr = array(  
             array("number"=>100,"name"=>"  ","title"=>"          ？？？") ,
    array("number"=>101,"name"=>"  ","title"=>"             ？？？") 
           ); 
/***********       *************/
// foreach ($arr as $key => $val) { 
//  if($val['name']=="  "){ 
//   $val['name']="  "; 
//  }
//  $arr[$key] = $val;//  
// } 
/***********       *************/
/***********       *************/
 foreach ($arr as $key => &$val) { 
  if($val['name']=="  "){ 
   $val['name']="  "; 
  }
 } 
/***********       *************/
 print_r($arr);