<?php
$response = array();
if ( !isset($_POST['email'], $_POST['password']) ) {
    $response['error'] = array(
        'msg'=>'missing POST parameter.',
        'details' => 'Recognized parameters were: '.join(', ', array_keys($_POST))
    );
}
else {
    $user = "root";
    $pass = "";
    $db = "uopuser";
    $con=mysqli_connect("localhost", $user, $pass, $db);

    if ( !$con ) {
        $response['error'] = array('error'=>'could not connect to database');
    }
    else if ( !($statement=mysqli_prepare($con, "SELECT fname, lname, email, `password` FROM User WHERE email = ? AND password = ?")) ) {
        $response['error'] = array('error'=>'could not prepare database query');
    }
    else if ( !mysqli_stmt_bind_param($statement, "ss", $_POST["email"], $_POST["password"]) ) {
         $response['error'] = array('error'=>'could bind parameters to statement');
    }
    else if ( !mysqli_stmt_execute($statement) ) {
        $response['error'] = array('error'=>'could execute database statement');
    }
    else if ( !mysqli_stmt_store_result($statement) ) {
        $response['error'] = array('error'=>'could not store database results');
    }
    else if ( !mysqli_stmt_bind_result($statement, $fname, $lname, $email, $password) ) {
        $response['error'] = array('error'=>'could not bind database results');
    }
    else {
        $result = mysqli_stmt_fetch($statement);
        if ( false===$result ) {
            $response['error'] = array('error'=>'error while fetching database results');
        }
        else if ( is_null($result) ) {
            $response['result'] = NULL; // no such user in database
        }
        else {
            $response['result'] = array(
                'fname'=>$fname,
                'lname'=>$lname,
                'email'=>$email,
                'password'=>$password
            );
        }
    }
}
header('Content-type: application/json');
echo json_encode($response);