jQuery autocomplete inside onKeyup function

I need to attach results from a jQuery function.

When the user types in the search field, a function is called and data is returned from my database.

I can see the returned data using alert function

<input type="text" name="symbol" id="symbol" required="required"  onkeyup="findmatch();">

The jQuery function called is below

function findmatch() {
  var symbol= document.getElementById("symbol").value;

  $.post("portfolio/searchStock.php",
      {
        search:symbol
      },
      function(data,status) {
        alert(data);
      });
}

I need the data returned to be attached as an autocomplete, I have tried using the following within the function.

I don't understand why it doesn't work

$( "#symbol" ).autocomplete({
                source: data
        });

The php file echoes data as below

    if (isset ($_POST['search'])){
        $search = $_POST['search'];
        if(!empty ($search)){
            $query="select * from companylist where symbol like '".mysql_real_escape_string($search)."%'";
            $query_run = mysql_query($query);

            while ($query_row = mysql_fetch_assoc($query_run)){
                $symbol = $query_row['symbol'];
                echo $symbol;
            }
        }
    }

You need to format the output of the db call:

while ($query_row = mysql_fetch_assoc($query_run)){
    $symbol[] = $query_row['symbol'];
}
echo json_encode($symbol);

Then, you need to parse the returned data.

var sourceData = [];
var arrData = $.parseJSON(data);
foreach(x in arrData)
{
    sourceData.push(arrData[x]);
}
$( "#symbol" ).autocomplete({
            source: sourceData
});