Escaped single character introducer instead of actual character - php

Question

For some reason \u009a is being sent to the xmlhttp.responseText and not \u0161, and I'm not sure why. I want š to be displayed in the textbox, but, instead, the single character introducer is being sent instead. Any ideas how I can fix this?
Main page code:
function loadDoc()
{
var xmlhttp;
// code for IE7+, Firefox, Chrome, Opera, Safari
if (window.XMLHttpRequest)
{
xmlhttp=new XMLHttpRequest();
}
// code for IE6, IE5
else
{
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function()
{
if (xmlhttp.readyState==4 && xmlhttp.status==200)
{
alert(xmlhttp.responseText);
var a = JSON.parse(xmlhttp.responseText);
document.getElementById("textbox").value=a.first;
document.getElementById("textbox2").value=a.second;
document.getElementById("textbox3").value=a.third;
document.getElementById("textbox4").value=a.fourth;
document.getElementById("textbox5").value=a.fifth;
document.getElementById("textbox6").value=a.sixth;
}
}
xmlhttp.open("GET","loadTextBox.php?id=4",true);
xmlhttp.send();
}
loadTextBox.php code:
<?php
header("Content-type: application/json");
---Placeholder for correct DB login info---
$result = $mysql->query(---Placeholder for correct SQL query---);
while ($row = $result->fetch_object())
{
$queryResult[] = $row->present_tense;
}
$textboxValue = $queryResult[0];
$textboxValue2 = $queryResult[1];
$textboxValue3 = $queryResult[2];
$textboxValue4 = $queryResult[3];
$textboxValue5 = $queryResult[4];
$textboxValue6 = $queryResult[5];
echo json_encode(array('first'=>utf8_encode($textboxValue),'second'=>
utf8_encode($textboxValue2),'third'=>utf8_encode($textboxValue3),'fourth'=>
utf8_encode($textboxValue4),'fifth'=>utf8_encode($textboxValue5),'sixth'=>
utf8_encode($textboxValue6)));
?>

Answer 1

Adding in the line $mysql->query("SET CHARACTER SET 'utf8'"); inside loadTextBox.php after connecting to the DB and before the SQL query and removing the lines with utf8_encode fixed it.