PHP数组没有正确格式化

I can't seem to figure out what the problem is, but my PHP array isn't outputting as proper JSON. I removed the json_encode function, only to find out that my array's are cascading and not properly formatting themselves. Here is an example of the output (with json_encode removed):

Array (
    [0] => Array (
        [username] => g4m3b0y
        [profile_photo] => default.png
        [email] => michael@me.com
        [first_name] => Michael
        [last_name] => Simpson
    )
) 
Array (
    [0] => Array (
        [username] => g4m3b0y
        [profile_photo] => default.png
        [email] => michael@me.com
        [first_name] => Michael
        [last_name] => Simpson
    )
    [1] => Array (
        [username] => michelle
        [profile_photo] => default.png
        [email] => michelle@gmail.com
        [first_name] => Michelle
        [last_name] => Houston
    )
)

As you can see, it's creating duplicate results in separate arrays, hence my issue with the JSON output. Here is my code which is generating the results:

    $sql2 = "SELECT DISTINCT username, profile_photo, first_name, last_name, email FROM users WHERE (
        first_name LIKE '%$q%'
        OR last_name LIKE '%$q%'
    ) ORDER BY last_name";

    $sq2 = mysql_query($sql2);
    $st2 = mysql_num_rows($sq2);

    if($st2>=1) {   
        while($a = mysql_fetch_array($sq2)) {
            $userRow[] = array(
                'username' => $a['username'],
                'profile_photo'   => $a['profile_photo'],
                'email'   => $a['email'],
                'first_name'   => $a['first_name'],
                'last_name'   => $a['last_name']
            );
        header('Content-Type: application/json');
        echo json_encode($userRow);
        }
    }

    else {
        exit;
    }

Your call to header and json_encode is inside your while loop. Move it outside and it'll compile the lot into one json string. At present it is outputting multiple separate ones.

This also explains why you're getting the duplicate too. Iteration one adds the first row to the array $userRow, it then outputs the result which has got the key 0. Then the second iteration adds the next row to the existing array, and therefore gets the key 1. Then it echos the json encoded string again, therefore printing 0 and 1 this time. Hence 0 then 0, then 1

$sql2 = "SELECT DISTINCT username, profile_photo, first_name, last_name, email FROM users WHERE (
    first_name LIKE '%$q%'
    OR last_name LIKE '%$q%'
) ORDER BY last_name";

$sq2 = mysql_query($sql2);
$st2 = mysql_num_rows($sq2);

if($st2>=1) {   
    while($a = mysql_fetch_array($sq2)) {
        $userRow[] = array(
            'username' => $a['username'],
            'profile_photo'   => $a['profile_photo'],
            'email'   => $a['email'],
            'first_name'   => $a['first_name'],
            'last_name'   => $a['last_name']
        );
    }

    // I moved this below the above }
    header('Content-Type: application/json');
    echo json_encode($userRow);
}

else {
    exit;
}