preg_replace和json_decode - Ajax处理程序 - php

I have problem with array in PHP. I've got that code in my Ajax handler PHP page:

if(isset($_GET['dataa']))
{
$dataa = $_GET['dataa'];
$dataa = preg_replace('/\\\"(.*?)\\\"/', '"$1"', $dataa);
$dataa = json_decode($dataa);
echo $dataa[0];
echo $dataa[1];
}

I tried to send data array in JavaScript to the Ajax handler but it's not working so I want to to pass param in the URL.

When I try to put this URL: ...AjaxHandler.php?dataa=["test1","test2"] I get this: test1test2 and that's ok.

But I don't really understand why I need to use preg_replace and json_decode. I tried to delete the preg_replace but then it didn't show me anything. I tried to delete the json_decode too but then I get only [/ on the screen.

I need to send multiple data so I do that with array.

Why I have to use preg_replace? Is it common to use preg_replace like that? All time when I send data array?