Php 如果assoc数组中缺少数组值，是否填充该数组值？

如果assoc数组中缺少数组值，是否填充该数组值？ 我有一个：

$A= array("A1"=>array("a"=>1,"b"=>2,"d"=>3),
          "A2"=>array("a"=>4,"b"=>3,"c"=>2,"d"=>1)
          );

基于A[“A2”]尺寸大于A[“A1”] 我想要新的$A看起来像这样

$A= array("A1"=>array("a"=>1,"b"=>2,"c"=>"0.00","d"=>3),
          "A2"=>array("a"=>4,"b"=>3,"c"=>2,"d"=>1)
          );

我会这样做：

if (count($A['A2']) > count($A['A1'])){
    foreach($A['A2'] as $key => $value){
        if (!array_key_exists($key, $A['A1'])){
             $A['A1'][$key] = '0.00';
        }
    }
}