Php PDO未插入数据库

无法查看数据未插入的原因。。。我有jQuery、HTML和PHP代码，它们都将发布在下面。我试过调试，但没用。谢谢

PHP代码：

<?php
include_once('db.php');
session_start();

    $message = $_POST['message'];

        if($message < 100 && $message > 2) {

            $insertMessage = $db->prepare("INSERT INTO `chats`(`time`, `message`, `username`) VALUES(:time, :message, :username)");

                $insertMessage->execute(array(

                        ':time'     => date("g:i a"),
                        ':message'  => $message,
                        ':username' => $_SESSION['username']

                    ));


        }
?>

HTML代码：

<form action="./php/send_chat.php" method="POST" class="chatForm">
<p class="field">
<input type="text" id="message" name="message" style="width: 275px;">
<span><button type="submit" id="chatBtn">Send</button>
</p>
</form>

发送

首先，使用硬编码参数简化插入，然后使用 ERRMODE_异常触发异常，允许您优雅地处理错误。 一旦生成了所需的结果，在每次修改之后，增量地修改代码检查。这是基本的调试

<?php
include_once("db.php");
$message ="Test Message";
$username = "username";
// connect to the database  
try {  
    $db = new PDO("mysql:host=$host;dbname=$database", $username, $password);  
    $db->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );  
    //
    $insertMessage = $db->prepare("INSERT INTO `chats`(`time`, `message`, `username`) VALUES(:time, :message, :username)");
    $insertMessage->execute(array(
        ':time'     => date("g:i a"),
        ':message'  => $message,
        ':username' => $username
        ));

  }   
catch(PDOException $e) {  
    echo "I'm sorry I'm afraid you can't do that.". $e->getMessage() ;// Remove or modify after testing 
}  

?>

---

您尝试了什么调试？似乎它根本无法与文件通信。。。我试着回显一些东西，但它没有显示在HTML中。不，没有错误。只是不插入数据库。为什么“测试后删除或修改”？为什么不让它过去而不被抓住呢？
<?php
include_once("db.php");
$message ="Test Message";
$username = "username";
// connect to the database  
try {  
    $db = new PDO("mysql:host=$host;dbname=$database", $username, $password);  
    $db->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );  
    //
    $insertMessage = $db->prepare("INSERT INTO `chats`(`time`, `message`, `username`) VALUES(:time, :message, :username)");
    $insertMessage->execute(array(
        ':time'     => date("g:i a"),
        ':message'  => $message,
        ':username' => $username
        ));

  }   
catch(PDOException $e) {  
    echo "I'm sorry I'm afraid you can't do that.". $e->getMessage() ;// Remove or modify after testing 
}  

?>