我有一个php脚本从一个表LABCPD中查询，其中有一个条目，但是POSTMAN中的GET调用返回状态OK，没有错误，但不返回任何数据，没有语法错误或权限/访问问题：
脚本：

<?php
/**
 * CPD Manual porject.
 * Files will be hosted on mooneycallans.com server
 * SQL inj. safe
 */

require_once 'headers.php';

// Add debugging output to console in POSTMAN and error log

error_reporting(E_ALL);
ini_set('error_reporting', 'E_ALL');

// Make suer the database on server we are reading / writing to as in UTF-8standard

   mysqli_set_charset('m558405_tests','utf8');
   


require_once 'headers.php';

// Create a connection to the databse 'm558405_tests DB 
$conn = new mysqli(hostName,usernamePlaceHolder,passwordPlaceHolder,databaseName);

$table = "LABCPD";

// Check DB connection and return  a JSON error if cannot connect

if ($conn->connect_error) {
    $errorResponse = array(
        'error' => 'Connection failed',
        'message' => $conn->connect_error
    );
    header('Content-Type: application/json');
    http_response_code(500); // Set the HTTP response code to indicate an internal server error
    echo json_encode($errorResponse);
    exit(); // Terminate the script
}


    if ($_SERVER['REQUEST_METHOD'] === 'GET'){
        if(isset($_GET['id'])) {
            /// Sfaely escape the user input and use a prepared statement
            $id = $conn->real_escape_string($_GET['id']);
    
            // Prepare an SQL statement with a placeholder
            $stmt = $conn->prepare("SELECT * FROM $table WHERE id = ?");
    
            // Bind the escaped user input to the placeholder in the SQL statement
            $stmt->bind_param("i",$id);
    
            // Execute the prepared statement
            $stmt->execute();
    
            // Get the result of the query
            $result = $stmt->get_result();
    
            // Fetch the data as an associative array
            $data = $result->fetch_assoc();
    
            // Close the prepared statement
            $stmt->close();
        } else {
            $data = array();
    
            // Prepare an SQL statement to fetch all rows
            $stmt = $conn->prepare("SELECT * FROM $table");
    
            // Execute prepared statement
            $stmt->execute();
    
            // Get the result of the query
            $result = $stmt->get_result();
    
            while ($d = $result->fetch_assoc()){
                $data[] = $d;
            }
    
            // Close the prepared statement
            $stmt->close();
        }
    
        // Return the JSON data
        exit(json_encode($data, JSON_THROW_ON_ERROR, 512));
    }

字符串
数据库有一个条目：x1c 0d1x
我的问题是，它看起来像是PHP代码片段的问题，还是我错过了其他东西？