I keep getting internal server error and do not know how or if my php files are set up right to respond correctly

My Titanium Code:

function artistInfo (e) {
 
  var artist_user_name = $.artist_user_name.value;
 
  var user_pass = $.user_pass.value;
 
  loginArtist(artist_user_name, user_pass);
 
}
 
$.login.addEventListener('click', artistInfo);
 
function loginArtist (artist_user_name, user_pass) {
 
var request = Titanium.Network.createHTTPClient();
 
  var artistloginURL0 = "http://104.237.146.221/loginartistlbi.php?action=checkartist&artist_user_name="+artist_user_name+"&user_pass="+user_pass;
 
request.open("GET", artistloginURL0);   
 
request.onload = function () {
 
  var arrData = [];
 
  arrData = eval('('+this.responseText+')');
 
  var result =arrData[0];
 
  if(result == "true"){
 
  Titanium.App.Properties.setString("artist_id",arrData[0].artist_id);
 
  var alrt_Success = Titanium.UI.createAlertDialog({
 
  title: 'Success!',
 
  message: 'You are now logged in.',
 
  buttonNames: ['OK']
 
  });
 
  alrt_Success.show();
 
  }else
 
  { var alrt_Sorry = Titanium.UI.createAlertDialog({
 
  title: 'Unsuccessful...',
 
  message: 'You do not have correct Artist Name and/or Password.',
 
  buttonNames:['OK']
 
  });
 
  alrt_Sorry.show();
 
  }};
 
  request.send();
 
}

<?php
 
switch($_GET['action'])
 
{
case  'createartist':
$DB_USER = "lbimind";
$DB_PASSWORD = "****";
$DB_HOST = "localhost";
$DB_NAME = "****";
 
$artist_user_name = $_GET['artist_user_name'];
$user_pass = md5(trim($_GET['user_pass']));
$artist_email = $_GET['artist_email'];
 
$resultArr = array();
$dbc = mysql_connect($DB_HOST, $DB_USER, $DB_PASSWORD);
$db = mysql_select_db($DB_NAME, $dbc);  
$query = mysql_query("SELECT * FROM artists WHERE artist_user_name = '$artist_user_name' AND user_pass = '$user_pass'",$dbc);
if(mysql_num_rows($query) >0) {
    $resultArr[0]['result'] = "another_artist";
}else {
    $query = mysql_query("INSERT INTO artists (artist_user_name, user_pass) VALUES ('$artist_user_name','$user_pass')",$dbc;
    if($query) {
        $resultArr[0]['result'] = "true";
    }else {
        $resultArr[0]['result'] = "false";
    }
}
 
echo json_encode($value($resultArr);
mysql_close($dbc);
break;
 
case 'checkartist': 
$DB_USER = "lbimind";
$DB_PASSWORD = "****";
$DB_HOST = "localhost";
$DB_NAME = "****";
 
$artist_user_name = $_GET['artist_user_name'];
$user_pass = md5(trim($_GET['user_pass']));
 
$resultArr = array();
$dbc = mysql_connect($DB_HOST, $DB_USER, $DB_PASSWORD);
$db = mysql_select_db($DB_NAME, $dbc);
$query = mysql_query("SELECT * FROM artists WHERE artist_user_name ='$artist_user_name' AND user_pass = '$user_pass'");
if(mysql_num_rows($query)>0) {
    $row = mysqli_fetch_array($query);
    $resultArr[0]['result'] = "true";
    $resultArr[0]['artist_id'] = $row['artist_id'];
    } else {
        $resultArr[0]['result'] = "false";
    }
    echo json_encode($resultArr);
    mysql_close($dbc);
break;
}
 
?>