未定义连接

Question

我有以下代码

    <?php
$host = "localhost";
$dbname = "hawkI";
$user = "root";
$password = "";

$userExist = false;
$userIP = null;
$userHasFinish = null;
$userLastPage = null;

try {
    $dbh = new PDO('mysql:host='.$host.';dbname='.$dbname, $user, $password);
} catch (PDOException $e) {
    echo 'Connection failed: ' . $e->getMessage();
}

function getIPforBDD(){
    return $_SERVER['REMOTE_ADDR'];
}

function UpdateUserProfile()
{
    $requete = "SELECT * FROM users WHERE ip = ".getIPforBDD();
    $result = $dbh->query($requete);

    if($resultat->rowCount() == 0)
        exit();

    foreach($result as $ligne)
    {       
        $userIP = $ligne['ip'];
        $userhasFinish = $ligne['finish'];
        $userLastPage = $ligne['lastPage'];
    }
}

function CheckUserPosition()
{
    UpdateUserProfile();
    if(!$userExist)
        AddUser();

    return GetUserStatus();
}

function GetUserStatus()
{
    $page;
    if($userHasFinish)
        $page = "end.php";
    else
        $page = $userLastPage;

    return $page;
}

function AddUser()
{
    $requete = "INSERT INTO users (ip, finish, lastPage) VALUES (".getIPforBDD().", ".false.", questionnaire_initial.php)";
    $result = $dbh->query($requete);
}

function SavePageInBDD($page){
    $requete = "UPDATE users SET lastPage = '.$page.' WHERE ip = ".getIPforBDD();
    $result = $dbh->query($requete);
} 
?>

但是，我用的时候有问题

( ! ) 注意：未定义变量：C:\wamp64\www\HawkI\bdd.php 中的 dbh 在第 66 行

我第一次使用 PHP 时并没有正确理解它是如何工作的，但我尝试了

global $dbh = new PDO('mysql:host='.$host.';dbname='.$dbname, $user, $password);

那也行不通。

此外，似乎放在函数之外的值不像在 js 中那样是全局的，我怎样才能让某些东西可以从任何地方访问（比如包含该文件的文件）

谢谢

Answer 1

你可以这样使用

$host = "localhost";
$dbname = "hawkI";
$user = "root";
$password = "";
$userExist = false;
$userIP = null;
$userHasFinish = null;
$userLastPage = null;
$dbh = NULL;
function db () {
    try {   
        if ($GLOBALS['dbh']===NULL){ 
            $GLOBALS['dbh'] = new PDO('mysql:host='.$host.';dbname='.$dbname, $user, $password);
        }
        return $GLOBALS['dbh'];    
    } catch (PDOException $e) {
        echo 'Connection failed: ' . $e->getMessage();
    }
}

function SavePageInBDD($page){
    $dbh = db();       
    $requete = "UPDATE users SET lastPage = '.$page.' WHERE ip = ".getIPforBDD();
    $result = $dbh->query($requete);
} 

Answer 2

要在函数中使用$dbh，您需要在函数范围内包含global关键字。

你可以在这里找到全局关键字解释http://php.net/manual/en/language.variables.scope.php#language.variables.scope.global

function AddUser()
{
    global $dbh;
    $requete = "INSERT INTO users (ip, finish, lastPage) VALUES (".getIPforBDD().", ".false.", questionnaire_initial.php)";
    $result = $dbh->query($requete);
}

Answer 3

更好的方法是这样做：

function getDB(){
  $dbh = null;
  try {
    $dbh = new PDO('mysql:host='.$host.';dbname='.$dbname, $user, $password);
   } catch (PDOException $e) {
      echo 'Connection failed: ' . $e->getMessage();
   }
   return $dbh;
}

比在你的函数中这样做：

function AddUser()
{
    $dbh = getDB();
    if(!is_null($dbh)){
         $requete = "INSERT INTO users (ip, finish, lastPage) VALUES (".getIPforBDD().", ".false.", questionnaire_initial.php)";
         $result = $dbh->query($requete);
    }
}