PHP中的Intersect / Diff数组

I have a problem using php like this:

Array 1: [a=>a, b=>b, c=c, d=d]

Array 2: [a=>123, b=>b, c=234]

ResultArray: [a=>123, c=>234, d=d]

How can I get ResultArray from Array1 & Array2? Can anyone help me. Thanks

$array1 = ['a'=>'a', 'b'=>'b', 'c'=>'c', 'd'=>'d'];
$array2 = ['a'=>'123', 'b'=>'b', 'c'=>'234'];
$diff_array = array_diff($array1,$array2);

$final = array_map(function($d) use ($array2){
    return isset($array2[$d]) ? $array2[$d] : $d;
}, $diff_array);

print_r($final);