Php JSON对MySQL结果中的数据进行编码

我没有从menucanhan.php？type=view获得任何数据。我的代码有问题吗？请帮我检查一下！太谢谢你了

db.php：从localhost继续数据

<?php
class DB {
    // Database credentials
    private $dbHost     = 'localhost';
    private $dbUsername = 'root';
    private $dbPassword = '';
    private $dbName     = 'thuctapcoso';
    public $db;

    public function __construct(){
        if(!isset($this->db)){
            // Connect to the database
            try{
                $conn = new PDO("mysql:host=".$this->dbHost.";dbname=".$this->dbName, $this->dbUsername, $this->dbPassword);
                $conn -> setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
                $this->db = $conn;
            }catch(PDOException $e){
                die("Failed to connect with MySQL: " . $e->getMessage());
            }
        }
    }

    public function getRows($table,$conditions = array()){
        $sql = 'SELECT ';
        $sql .= array_key_exists("select",$conditions)?$conditions['select']:'*';
        $sql .= ' FROM '.$table;
        if(array_key_exists("where",$conditions)){
            $sql .= ' WHERE ';
            $i = 0;
            foreach($conditions['where'] as $key => $value){
                $pre = ($i > 0)?' AND ':'';
                $sql .= $pre.$key." = '".$value."'";
                $i++;
            }
        }

        if(array_key_exists("order_by",$conditions)){
            $sql .= ' ORDER BY '.$conditions['order_by']; 
        }

        if(array_key_exists("start",$conditions) && array_key_exists("limit",$conditions)){
            $sql .= ' LIMIT '.$conditions['start'].','.$conditions['limit']; 
        }elseif(!array_key_exists("start",$conditions) && array_key_exists("limit",$conditions)){
            $sql .= ' LIMIT '.$conditions['limit']; 
        }

        $query = $this->db->prepare($sql);
        $query->execute();

        if(array_key_exists("return_type",$conditions) && $conditions['return_type'] != 'all'){
            switch($conditions['return_type']){
                case 'count':
                    $data = $query->rowCount();
                    break;
                case 'single':
                    $data = $query->fetch(PDO::FETCH_ASSOC);
                    break;
                default:
                    $data = '';
            }
        }else{
            if($query->rowCount() > 0){
                $data = $query->fetchAll(PDO::FETCH_ASSOC);
            }
        }

        return !empty($data)?$data:false;
    }
}
?>

///////////////////////////////////////////////////////////////////////////////////

menucanhan.php：

<?php
include 'db.php';
$db = new DB();
$tblName = 'menucanhan';
if(isset($_REQUEST['type']) && !empty($_REQUEST['type'])){
    $type = $_REQUEST['type'];
    switch($type){
        case "view":
            $records = $db->getRows($tblName);
            if($records){
                $data['records'] = $db->getRows($tblName);  
                $data['status'] = 'OK';
            }else{
                $data['records'] = array();
                $data['status'] = 'ERR';
            }
            echo json_encode($data);
            break;        
        default:
            echo '{"status":"INVALID"}';
    }
}
?>

您应该先进行一些广泛的调试。在流中的不同点回显数据位，并隔离问题所在的位置与预期的工作状态。尝试回显getRows函数中的sql语句验证表是否为空，因为函数仅在存在行时返回如果您确实编写了该类，您应该能够轻松地调试它。您应该更好地利用PDO调用，并使用占位符保护查询免受注入攻击。