got stuck converting MySql output in JSON array with php

I am making an iphone app. a part of that app allows users to search for a company on location.

I have a MySql database containing the companies that can be searched for, and a php file on my website to receive the searched data, and to return the companyName and companyLocation for all the found companies to my app. it looks like this:

<?php

if (isset($_GET["companyCitySearchField"])){
                $companyCity = $_GET["companyCitySearchField"];
                $result = search($companyCity);
                echo $result;
        }

function makeSqlConnection()
{
$DB_HostName = "******";
$DB_Name = "*******";
$DB_User = "*******";
$DB_Pass = "*******";


    $con = mysql_connect($DB_HostName,$DB_User,$DB_Pass) or die(mysql_error()); 
    mysql_select_db($DB_Name,$con) or die(mysql_error()); 

    return $con;
}

function disconnectSqlConnection($con)
{
    mysql_close($con);
}

function search($companyCity)
{
    $con = makeSqlConnection(); 
    $query = mysql_query("SELECT companyName, companyCity from Company  WHERE companyCity = '$companyCity'");
    $companies = array();
        while ($row = mysql_fetch_assoc($query)) {
        $companies['companies'][] = $row;
        print json_encode($companies);
    }   
    disconnectSqlConnection($con);  
}

?>

this works fine when only one company is found. it gives me a perfect JSON array:

{"companies":[{"companyName":"Dijkstra","companyCity":"Geldermalsen"}]}

everything fine so far.

Now, I create another company in my database, also with Geldermalsen as location.

2 companies are found in the database now. the JSON array it return now, doesn't make sense:

{"companies":[{"companyName":"Dijkstra","companyCity":"Geldermalsen"}]}{"companies":[{"companyName":"Dijkstra","companyCity":"Geldermalsen"},{"companyName":"testaccount","companyCity":"Geldermalsen"}]}

for some reason, it seems to make 2 separate array's. one for the first found company, and one with both.

I have been searching the web, stackoverflow, google and even the book 'PHP and MySql for dummies' for days, and I have changed my code numerous times, and whatever I try it keeps on doing this.

Does anyone know what I should do to get one array containing all found companies with this script, instead of these 2?

any help would be very welcome, Thank you in advance!