从serialize（）AJAX中获取PHP中的多个/多个POST变量的最佳方法是什么？

I have a form with many many inputs and I use the following code to send all my form data to php proccesing:

HTML:

<form>
<input type="text" name="a" />
<input type="text" name="b" />
<input type="text" name="c" />
<input type="text" name="d" />
<input type="text" name="e" />
<input type="text" name="f" />
<button type="button" onclick="update()">UPDATE</button>
</form>

<!-- HERE I SHOW THE VALUES FROM ABOVE INPUTS -->
<input type="text" id="a" />
<input type="text" id="b" />
<input type="text" id="c" />
<input type="text" id="d" />
<input type="text" id="e" />
<input type="text" id="f" />

JS:

<script>
function update()
{
    var str = $("form").serializeArray();
    $.ajax({  
        type: "POST",  
        url: "update.php",  
        data: str,  
        dataType: 'json',
        success: function(result) 
        {  
            document.getElementById("a").value = result.a;
            document.getElementById("b").value = result.b;
            document.getElementById("c").value = result.c;
            document.getElementById("d").value = result.d;
            document.getElementById("e").value = result.e;
            document.getElementById("f").value = result.f;
        },
        error: function(result){
            console.log("Error:");
            console.log(result);
        }
    });
    // return false;
}

</script>

AND update.php:

<?php
$a = $_POST['a'];
$b = $_POST['b'];
$c = $_POST['c'];
$a = $_POST['d'];
$b = $_POST['e'];
$c = $_POST['f'];

$arr = array(
'a' => $a, 
'b' => $b, 
'c' => $c,
'a' => $d, 
'b' => $e, 
'c' => $f
);

echo json_encode($arr);

?>

1. First question: Is there a simple method of passing all serialize() variables in PHP, instead of writing all of them like I did in my code? There are too many and I think is is not OK that I have to manually add all of them.

    $a = $_POST['a'];
    $b = $_POST['b'];
    $c = $_POST['c'];
    $d = $_POST['d'];
    $e = $_POST['e'];
    $f = $_POST['f'];
   

2. Is there a short way to pass ajax result array values from PHP in multiple inputs, instead of using the following code?

document.getElementById("a").value = result.a;
 document.getElementById("b").value = result.b;
 document.getElementById("c").value = result.c;
 document.getElementById("d").value = result.d;
 document.getElementById("e").value = result.e;
 document.getElementById("f").value = result.f;

All I am trying to say that I have too many inputs on the form and I don't want to add those variables manually. It takes too much time and it is easy to mistake at getting id's and names.

You can pass your form inputs as array instead of individual name.. Meaning

<input name='form[a]' type='text'/>
 <input name='form[b]' type='text'/>
 <input name='form[c]' type='text'/>
 <input name='form[d]' type='text'/>

Then in php do this

echo(json_encode($_POST['form']));