Upload an image to MYSQL from ANDROID with a PHP webservice

Android:

private String convertirimagen(Bitmap bitmap){
    ByteArrayOutputStream stream = new ByteArrayOutputStream();
    bitmap.compress(Bitmap.CompressFormat.PNG,70,stream);
    byte[] bytes = stream.toByteArray();
    return Base64.encodeToString(bytes,Base64.NO_WRAP);
}

PHP:

    $v1 = $mysqli->real_escape_string($_REQUEST['1']);
    $v2 = $mysqli->real_escape_string($_REQUEST['2']);
    $v3 = $mysqli->real_escape_string($_REQUEST['3']);
    $v4 = $mysqli->real_escape_string($_REQUEST['4']);
    $v5 = $mysqli->real_escape_string($_REQUEST['5']);
    $v6 = $mysqli->real_escape_string($_REQUEST['6']);
    $v7 = $mysqli->real_escape_string($_REQUEST['7']);
    $v8 = $mysqli->real_escape_string(base64_decode($_REQUEST['8']));

    $rf1 = f1($v1,$v2,$v3,$v4,$v5,$v6,$v7,$v8);

This does not work:

function f1($v1,$v2,$v3,$v4,$v5,$v6,$v7,$v8){
global $mysqli;
$data=array();

$stmt = $mysqli->prepare("INSERT INTO 'usuarios'('codigo', 'nombres', 'apellidop', 'apellidom', 'foto', 'correo', 'password', 'ntelefono', 'activo', 'tipouser') VALUES (?,?,?,?,?,?,?,?,?,?)");
$a = 1;
$t = 2;
$null = null;
$stmt->bind_param('isssbssiii',$v1,$v2,$v3,$v4,$null,$v5,$v6,$v7,$a,$t);
$stmt->send_long_data(4, $v8);
if ($stmt->execute()){

    $data [] = array('mensaje'=>'Registrado con exito');
    return $data;
}}

But here normal runs:

function f1($v1,$v2,$v3,$v4,$v5,$v6,$v7,$v8){
global $mysqli;
$data=array();

$stmt = $mysqli->prepare("INSERT INTO 'usuarios'('codigo', 'nombres', 'apellidop', 'apellidom', 'foto', 'correo', 'password', 'ntelefono', 'activo', 'tipouser') VALUES (?,?,?,?,'$v8',?,?,?,?,?)");
$a = 1;
$t = 2;
$stmt->bind_param('isssssiii',$v1,$v2,$v3,$v4,$v5,$v6,$v7,$a,$t);
if ($stmt->execute()){

    $data [] = array('mensaje'=>'Registrado con exito');
    return $data;
}}