无法加载资源：服务器响应状态为500（内部服务器错误）Web服务器php

Question

<?php
require("MySQLDAO.php");
$config = parse_ini_file('../database.ini');
$returnValue = array();
//checking if the information is not empty.
if(empty($_REQUEST["firstname"]) || empty($_REQUEST["lastname"]) 
        || empty($_REQUEST["address"])|| empty($_REQUEST["postcode"])|| empty($_REQUEST["userid"])){
    $returnValue["error"]="Missing information";
    $returnValue["message"]="You have not added all the information needed to sign up.";
    echo json_encode($returnValue);
    return;
}
//protect from sql injections.
$fn = htmlentities($_REQUEST["firstname"]);
$ln = htmlentities($_REQUEST["lastname"]);
$add = htmlentities($_REQUEST["address"]);
$post = htmlentities($_REQUEST["postcode"]);
$userid = htmlentities($_REQUEST["userid"]);
// read ini file which has the keys.
$dbhost = trim($config["dbhost"]);
    $dbuser = trim($config["dbuser"]);
    $dbpass = trim($config["dbpass"]);
    $dbname = trim($config["dbname"]);
    $dao = new MySQLDAO($dbhost,$dbuser,$dbpass,$dbname);
    $dao ->openConnection();
$userdetails = $dao->postAccDetail($userid);
if (!empty($userdetails))
{
 $returnValue["error"]="Error 101";
    $returnValue["message"]="You have already submitted to get your accounts through the post.";
    echo json_encode($returnValue);
    return;
}
//register new user. 
$result = $dao ->registerPost($fn,$ln,$add,$post,$userid);
if($result){
$returnValue["Message1"] = "Congratulations!";
$returnValue["Message2"] = "We will be sending your details to you in the next 5 working days.";
}
else{
$returnValue["error"] = "Something went wrong";
$returnValue["Message"] = "Sorry we could not create a profile for you please try again.";
}
$dao ->closeConnection();
echo json_encode($returnValue);
?>

<database file>
 public function postAccDetail($userid) {
     $returnValue = array();
     $sql = "select * from post where userid ='".$userid."'";
        $result = $this->conn->query($sql);
        if ($result != null && (mysqli_num_rows($result) >= 1)) {
                     $row = $result->fetch_array(MYSQLI_ASSOC);
            if (!empty($row)) {
                $returnValue = $row;
            }
        }
        return $returnValue;
    }
    public function registerPost($fn,$ln,$add,$post,$userid) {
    $sql = "insert into post set firstname=?,lastname=?,address=?,postcode=?,userid=?";
      $statement = $this->conn->prepare($sql);
    if (!$statement)
            throw new Exception($statement->error);
    //the 5s indicate that the values are going to be strings. 
    $statement->bind_param("ssssi",$fn,$ln,$add,$post,$userid);
     $returnValue = $statement->execute();

        return $returnValue;  


    }

我似乎无法使用此代码发现错误，并且想知道是否有人可以提供帮助。当我在我的本地机器上运行该文件时，我似乎很好但是当我将文件上传到服务器时，我似乎无法加载资源我知道数据库文件是正确的，因为其他文件似乎没有问题。

I've added an image of the database aswell.

有人可以帮助我。