Call AJAX to populate form fields from mysql database when an input is given

I have made form in which I want to give the ID of an order in a specific field and AJAX will fetch data from database and autofill the remaining fields as per database info.

Here is my FORM –

<form name="confirm_order_entry_form" method="post" action="<?php echo htmlspecialchars($_SERVER['PHP_SELF']);?>">
      
      <div class="form_data">
         <label>Projection Code :</label>
         <input type="text" name="projection_code" onchange="projection_code_data_fetch(this.value)">
      </div>
      <div class="form_data">
         <label>Marketing By :</label>
         <input type="text" name="c_marketing_person" id="marketingPerson">
      </div>
      <div class="form_data">
         <label>Factory Name :</label>
         <input type="text" name="c_factory_name" id="factoryName">
      </div>
      <input type="submit" value="submit" name="submit">
</form>

Here is my javascript function –

function projection_code_data_fetch(input_data){

    if (input_data==""){
        return;
    }
    if (window.XMLHttpRequest){// code for IE7+, Firefox, Chrome, Opera, Safari
        xmlhttp=new XMLHttpRequest();
    }else{// code for IE6, IE5
        xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
    }

    xmlhttp.onreadystatechange=function(){
        if (xmlhttp.readyState==4 && xmlhttp.status==200){
            var data = JSON.parse(xmlhttp.responseText);
            for(var i=0;i<data.length;i++){
              document.getElementById("marketingPerson").value = data[i].name;
              document.getElementById("factoryName").value = data[i].factory;
            }
        }
    }

    xmlhttp.open("GET","formUp.php?q="+input_data,true);
    xmlhttp.send();

}

And here is formUp file –

<?php

$servername='localhost';
$username='root';
$password='';
$dbname = "xcel-erp";
$conn=mysqli_connect($servername,$username,$password,"$dbname");

if(!$conn){
    die('Could not Connect MySql Server:' .mysql_error());
}

$q = intval($_GET['q']);

$sql="SELECT * FROM projectiondatabase WHERE System_ID = '".$q."'";

$result = mysqli_query($conn,$sql);
$info = array();
while($row = mysqli_fetch_array($result)){
    $cMarketingPerson = $row['MarketingPerson'];
    $cFactoryName = $row['FactoryName'];
    $info[] = array( 'name' => $cMarketingPerson, 'factory' => $cFactoryName);
}
echo json_encode($info);

?>

I have run the javascipt & formUp file individually. Both are running fine. But the actual output is not coming when combined.

Please help!