通过PHP搜索时，Jquery自动完成的最大限制是多少？

I have an .aspx page which uses the jquery autocomplete to search a SQL database via php. The issue is the database column 'Contact' has hundreds records with the users first name 'Peter' so when I type 'Peter' I get no results until a start typing a letter of their surname. How do I get all the results to appear? It works fine when there are smaller results e.g. 'John', I also want to retain the autocomplete minLength as 3.

I've tried to change the PHP.ini max_input_vars from the default 1000 and reset IIS but that didn't work.

jquery code

$(function () {
    $("#queryString").autocomplete({
        source: function(request, response) {
            $.ajax({
            url: "Search.php",
            data: { term: $("#queryString").val(), searchby: $("#ddlSearch").val()},
            dataType: "json",
            type: "GET",
                success: function(data){
                response(data);
                }
            });
        },
        minLength: 3,
        multiple: true, 
        multipleSeparator: " "
    })
});

PHP file

$tsql = "SELECT [Contact] FROM [Goldmine].[dbo].[CONTACT1] WHERE [Contact] LIKE '$queryString%'";
}

If ($ddlSearch == 'Name') {

$stmt = sqlsrv_query( $conn, $tsql); 
$data = array();
while( $row = sqlsrv_fetch_array( $stmt, SQLSRV_FETCH_NUMERIC))     
{   
$data = array_merge( $data, array_values($row) );
sort($data, SORT_NATURAL | SORT_FLAG_CASE);
}
echo json_encode($data);