Php CodeIgniter检查数据库是否错误

我正在开发一个连接到数据库并从表中检索数据的小应用程序。但是我需要向调用者显示我无法连接到指定的主机。我怎样才能做到这一点？我尝试使用此代码段，但它不起作用：

define('ERROR_STR', 'ERROR: ');
# ...
if ($this->db->_error_number() OR $this->db->_error_message()) {
    die(ERROR_STR . $this->db->_error_number() . ': ' . $this->db->_error_message());
}

在我的日志中，我列出了以下内容：

ERROR - 2015-04-09 15:18:19 --> Severity: Warning  --> mysqli_connect(): (HY000/2005): Unknown MySQL server host 'localhosta' (2)

但我需要在运行时检查（显然，在尝试连接之后）数据库配置参数是否错误（主机/用户/密码），并将错误消息回显给调用者$这个->数据库->错误号（）和$this->数据库->错误号（）没有给我那个错误消息。 有什么想法吗？希望我说得够清楚。谢谢

编辑：

这是我的数据库配置：

$db['default']['hostname'] = 'localhost';
$db['default']['username'] = '';
$db['default']['password'] = '';
$db['default']['database'] = '';
$db['default']['dbdriver'] = 'mysql';
$db['default']['dbprefix'] = '';
$db['default']['pconnect'] = TRUE;
$db['default']['db_debug'] = FALSE;
$db['default']['cache_on'] = FALSE;
$db['default']['cachedir'] = '';
$db['default']['char_set'] = 'utf8';
$db['default']['dbcollat'] = 'utf8_general_ci';
$db['default']['swap_pre'] = '';
$db['default']['autoinit'] = FALSE;
$db['default']['stricton'] = FALSE;

但它被合并到我的控制器中的真实db config数组中：

    $this->connected = false;

    $this->load->database(array_merge(array(
        'hostname' => "localhost",
        'username' => "username",
        'password' => "password",
        'database' => "database",
        'dbdriver' => "mysqli",
        'dbprefix' => "",
        'pconnect' => FALSE,
        'db_debug' => FALSE,
        'cache_on' => FALSE,
        'cachedir' => "",
        'char_set' => "utf8",
        'dbcollat' => "utf8_general_ci",
                    ), (array) $json->conn), TRUE);

    if ($this->db->initialize() !== FALSE) {
        die('Not CONNECTED!');
    }

    $this->connected = true;

$this->connected = false;

$this->load->database(array_merge(array(
    'hostname' => "localhost",
    'username' => "root",
    'password' => "root",
    'database' => "automaserv",
    'dbdriver' => "mysqli",
    'dbprefix' => "",
    'pconnect' => FALSE,
    'db_debug' => FALSE,
    'cache_on' => FALSE,
    'cachedir' => "",
    'char_set' => "utf8",
    'dbcollat' => "utf8_general_ci",
), (array) $json->conn));

if ($this->db->initialize() === FALSE) {
    die('Not CONNECTED!');
}

$this->connected = true;

但是我的日志中有一个错误

if ($this->db->initialize() !== FALSE) {

说

ERROR - 2015-04-09 15:47:48 --> Severity: Notice  --> Undefined property: Main::$db /.../.../...

---

我不知道出了什么问题

您可以将初始连接放入try-catch块

try{
   $this->load->database(array_merge(array(
    'hostname' => "localhost",
    'username' => "username",
    'password' => "password",
    'database' => "database",
    'dbdriver' => "mysqli",
    'dbprefix' => "",
    'pconnect' => FALSE,
    'db_debug' => FALSE,
    'cache_on' => FALSE,
    'cachedir' => "",
    'char_set' => "utf8",
    'dbcollat' => "utf8_general_ci",
                ), (array) $json->conn), TRUE);

} catch (exception $e){
    echo "can't connect";

}

---

删除

$this->load->database

（默认为

FALSE

）的最后一个参数确实完成了剩余的工作

这是来自控制器的新代码：

    $this->connected = false;

    $this->load->database(array_merge(array(
        'hostname' => "localhost",
        'username' => "username",
        'password' => "password",
        'database' => "database",
        'dbdriver' => "mysqli",
        'dbprefix' => "",
        'pconnect' => FALSE,
        'db_debug' => FALSE,
        'cache_on' => FALSE,
        'cachedir' => "",
        'char_set' => "utf8",
        'dbcollat' => "utf8_general_ci",
                    ), (array) $json->conn), TRUE);

    if ($this->db->initialize() !== FALSE) {
        die('Not CONNECTED!');
    }

    $this->connected = true;

$this->connected = false;

$this->load->database(array_merge(array(
    'hostname' => "localhost",
    'username' => "root",
    'password' => "root",
    'database' => "automaserv",
    'dbdriver' => "mysqli",
    'dbprefix' => "",
    'pconnect' => FALSE,
    'db_debug' => FALSE,
    'cache_on' => FALSE,
    'cachedir' => "",
    'char_set' => "utf8",
    'dbcollat' => "utf8_general_ci",
), (array) $json->conn));

if ($this->db->initialize() === FALSE) {
    die('Not CONNECTED!');
}

$this->connected = true;

---

谢谢。

“未知的MySQL服务器主机'localhosta'”对于无效的数据库连接配置集$db['default']['db_debug']=FALSE是一条非常明确的消息；显示error@Cristik，是的，但我想在我的控制器中获取该消息，以便向用户显示它。不知道这是如何或何时写入日志的没有什么，如您仍然看到错误或您没有看到“无法连接”？我说的“什么都没有发生”是指问题仍然存在。但现在它是固定的，正如我在回答中提到的。无论如何，谢谢你。