サーバーの[500]エラーの原因がわからないです

#問題点
jqueryの$.postで値を渡そうとすると、500エラーが発生してしまいます。
原因はCountup.phpにあるみたいなのですが、自分には問題があるようには見えません。
どこが原因でエラーが発生しているのでしょうか？

#ソースコード

mysql
1[Thu Nov 29 12:52:44 2018] 192.168.33.1:53097 [500]: /Countup.php

php
1<?php
2
3ini_set('display_errors', 1);
4
5define('MAX_FILE_SIZE', 1 * 1024 * 1024); //1MB
6define('THUMBNAIL_WIDTH', 400);
7define('IMAGES_DIR', __DIR__ . '/images');
8define('THUMBNAIL_DIR', __DIR__ . '/thumbs');
9
10if (!function_exists('imagecreatetruecolor')) {
11  echo "GD not installed";
12  exit;
13}
14
15
16require 'ImageUploader.php';
17
18$uploader = new \MyApp\ImageUploader();
19
20if($_SERVER['REQUEST_METHOD'] === 'POST') {
21  $uploader->upload();
22}
23
24list($success, $error) = $uploader->getResults();
25
26$images = $uploader->getImages();
27
28
29require_once(__DIR__ . '/Login/config/config.php');
30
31// ユーザーデータ取得
32require_once(__DIR__ . '/Login/lib/Controller/Index.php');
33
34$app = new \MyApp\Controller\Index();
35$app->run();
36
37
38 ?>
39
40
41 <!DOCTYPE html>
42 <html lang="ja">
43   <head>
44     <meta charset="utf-8">
45     <title>**</title>
46     <link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.4.1/css/all.css" integrity="sha384-5sAR7xN1Nv6T6+dT2mhtzEpVJvfS3NScPQTrOxhwjIuvcA67KV2R5Jz6kr4abQsz" crossorigin="anonymous">
47     <link rel="stylesheet" href="styles.css">
48   </head>
49
50   <body>
51
52     <header class="bg">
53       <div class="container">
54         <h1>HAIR</h1>
55       </div>
56       <div class="logined">
57         <p class="mypage"><a href="mypage.php"><i class="fas fa-user-circle"> My Page </i></a></p><br>
58         <span class="mypage user" id="<?= $app->me()->id;  ?>"><?= h($app->me()->email); ?></span>
59       </div>
60     </header>
61
62
63     <!-- ** -->
64     <section class="feature">
65       <div class="container">
66         <h1 data-subtitle="- New Arrival -"><a href="">**</a></h1>
67       </div>
68     </section>
69
70     <section class="images">
71       <ul class="img_row">
72         <?php
73           $sql = "SELECT * FROM posts ORDER BY id desc;";
74           $stmt = $pdo->prepare($sql);
75           $stmt -> execute();
76           while ($row = $stmt -> fetch(\PDO::FETCH_ASSOC)):
77          ?>
78         <li>
79           <?php
80           echo ("<a href='/images/$row[file_name]'>");
81           echo ("<img src='/thumbs/$row[file_name]' class='img' id ='$row[id]'></a>");
82           echo ("<div class='heart icon' id='icon_$row[id]'></div>");
83           echo ("<div class='likes_count' id='likes_count_$row[id]'>  $row[user_id] </div>");
84           ?>
85         </li>
86         <?php endwhile; ?>
87       </ul>
88     </section>
89
90   <footer class="bg">
91     <p>&copy; hair.com</p>
92   </footer>
93
94       <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
95       <script>
96       $(function() {
97         'use strict';
98
99         $( '.icon' ).on( 'click', function() {
100            var $_t = $( this );
101            var $_u = $('.user');
102            $_t.css( 'color', 'red' );
103            $.post( 'Countup.php', {
104                post_id: $_t.parent().find( 'img' ).attr( 'id' ),
105                user_id: $_u.parent().find('span').attr('id')
106            }, function( data ) {
107                $_t.parent().find( '.likes_count' ).text( data );
108            } );
109          } );
110
111       });
112
113       </script>
114   </body>
115 </html>
116

php
1<?php
2
3ini_set('display_errors', 1);
4error_reporting(E_ALL);
5
6require_once(__DIR__ . '/Login/config/config.php');
7require_once(__DIR__ . '/Like.php');
8
9$likeApp = new \MyApp\Like();
10
11
12if ($_SERVER['REQUEST_METHOD'] === 'POST') {
13  try {
14
15    $res = $likeApp->post();
16    echo $res;
17
18    // header('Content-Type: application/json');
19    // echo json_encode($res);
20    // exit;
21
22  } catch (Exception $e) {
23    header($_SERVER['SERVER_PROTOCOL'] . ' 500 Internal Server Error', true, 500);
24    echo $e->getMessage();
25    exit;
26  }
27}
28
29?>
30

php
1<?php
2
3namespace MyApp;
4
5class Like {
6
7	private $pdo;
8
9	public function __construct() {
10		try {
11			$dsn = "mysql:dbhost=localhost;dbname=***";
12			$username = "***";
13			$password = "***";
14			$this->pdo = new \PDO($dsn, $username, $password);
15			$this->pdo->setAttribute(\PDO::ATTR_ERRMODE, \PDO::ERRMODE_EXCEPTION);
16
17		} catch (\PDOException $e) {
18			echo $e->getMessage();
19			exit;
20		}
21	}
22
23	public function post() {
24
25		if (!isset($_POST['post_id'])) {
26			throw new \Exception('post_id not set!');
27		}
28
29		if (!isset($_POST['user_id'])) {
30			throw new \Exception('user_id not set!');
31		}
32
33
34		$post_id = $_POST['post_id'];
35		$user_id = $_POST['user_id'];
36
37		$this->pdo->beginTransaction();
38
39		$sql = "INSERT INTO likes (post_id, user_id) values (:post_id, :user_id)";
40		$stmt = $this->pdo->prepare($sql);
41		$stmt->bindValue(":post_id", $post_id, \PDO::PARAM_INT);
42		$stmt->bindValue(":user_id", $user_id, \PDO::PARAM_INT);
43		$stmt->execute();
44
45		$sql = "UPDATE posts set user_id = user_id+1 where id = :id";
46		$stmt = $this->pdo->prepare($sql);
47		$stmt->bindValue(":id", $post_id, \PDO::PARAM_INT);
48		$stmt->execute();
49		$result = $stmt->fetch(\PDO::FETCH_ASSOC);
50
51		$this->pdo->commit();
52
53
54		echo $result['user_id'];
55
56	}
57}
58
59?>
60