PHP Select with PDO Call to a member function prepare() on a non-object error

问题

I'm getting a Call to a member function prepare() on a non-object error in my PHP when using PDO to select data that was sent via an AJAX call.

Searching around on StackOverflow I've found many answers to this error, but none work to fix my problem.

The weird part is that the other PHP files use the same PDO calls and work successfully, but this one is giving me the non-object error only.

To note, the PDO connection is identical to the other pages where it works, so I know that's not causing the problem.

Also, I have tested that the AJAX data sent is being received, and that is working too.

PHP Code

$mysql_user = "NotTelling";
$mysql_password = "DefinatelyNotThis";
try
{
    $dbh = new PDO("mysql:host=somehost;dbname=somename", $mysql_user, $mysql_password);
    $dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    $username = $_POST['username'];
    $inPword = $_POST['password'];
    $lat =  $_POST['lat'];
    $lon =  $_POST['lon'];

    $loggedin = "";
    $password_hash = "";
    $loggedinstatus = "";
    $pts = "";

    function getLoginInfo()
    {
        $sth = $dbh -> prepare('SELECT pword, loggedin, points FROM login WHERE uname = :uname');
        $sth->bindParam(':uname', $username, PDO::PARAM_STR);
        while($row = $sth->fetch(PDO::FETCH_ASSOC))
        {
            echo $row['pword'];
            echo $row['loggedin'];
            echo $row['points'];
        }
        $password_hash = $fetch['pword'];
        $loggedinstatus = $fetch['loggedin'];
        $pts = $fetch["points"];

        if($password_hash === null || $loggedinstatus === null || $pts === null)
        {
            die(json_encode(array("message" => "none")));
        }
        else
        {           
            return "more";
        }
    }

    function checkLoginCreds()
    {
        if(crypt($inPword, $password_hash) === $password_hash)
        {
            switch($loggedinstatus)
            {
                case  "no":         
                    $sel = $dbh->prepare("UPDATE login SET loggedin='yes' WHERE uname = ?");
                    $sel->execute(array($username));
                    return "AllGood";
                    break;

                defaut:
                    return "alreadyin";
                    break;
            }
        }
        else
        {
            return "BadLogin";
        }
    }

    if(getLoginInfo() === "more")
    {
        echo json_encode(array("message" => checkLoginCreds()));
    }

    getLoginInfo();
}
catch(PDOException $e)
{
    echo $e->getMessage();
    file_put_contents('PDOErrors.txt', $e->getMessage(), FILE_APPEND);
}

Finally, here's the output when I var_dump() the PDO connection.

object(PDO)#1 (0) {}

回答1:

For this to work, you need to use the global variable scope, explained here: http://php.net/manual/en/language.variables.scope.php

$mysql_user = "NotTelling";
$mysql_password = "DefinatelyNotThis";
try
{
    $dbh = new PDO("mysql:host=somehost;dbname=somename", $mysql_user, $mysql_password);
    $dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    $username = $_POST['username'];
    $inPword = $_POST['password'];
    $lat =  $_POST['lat'];
    $lon =  $_POST['lon'];

    $loggedin = "";
    $password_hash = "";
    $loggedinstatus = "";
    $pts = "";

    function getLoginInfo()
    {
        global $dbh, $username, $password_hash, $loggedinstatus, $pts;

        $sth = $dbh -> prepare('SELECT pword, loggedin, points FROM login WHERE uname = :uname');
        $sth->bindParam(':uname', $username, PDO::PARAM_STR);
        while($row = $sth->fetch(PDO::FETCH_ASSOC))
        {
            echo $row['pword'];
            echo $row['loggedin'];
            echo $row['points'];
        }
        $password_hash = $fetch['pword'];
        $loggedinstatus = $fetch['loggedin'];
        $pts = $fetch["points"];

        if($password_hash === null || $loggedinstatus === null || $pts === null)
        {
            die(json_encode(array("message" => "none")));
        }
        else
        {           
            return "more";
        }
    }

    function checkLoginCreds()
    {
        global $dbh, $inPword, $password_hash, $loggedinstatus, $username;

        if(crypt($inPword, $password_hash) === $password_hash)
        {
            switch($loggedinstatus)
            {
                case  "no":         
                    $sel = $dbh->prepare("UPDATE login SET loggedin='yes' WHERE uname = ?");
                    $sel->execute(array($username));
                    return "AllGood";
                    break;

                defaut:
                    return "alreadyin";
                    break;
            }
        }
        else
        {
            return "BadLogin";
        }
    }

    if(getLoginInfo() === "more")
    {
        echo json_encode(array("message" => checkLoginCreds()));
    }

    getLoginInfo();
}
catch(PDOException $e)
{
    echo $e->getMessage();
    file_put_contents('PDOErrors.txt', $e->getMessage(), FILE_APPEND);
}

But this can get messy very quickly.

I suggest you put the variables in an array or using OOP for a more robust solution: http://php.net/manual/en/language.oop5.php

回答2:

This is how you can define it in a class..

class someClass {

  private $db;

  public function __construct(){


            $this->dbconnect();

    }

    private function dbconnect() {

      try { //try connection

        $dbh = new PDO('mysql:host=localhost;dbname=somenane', 'usernane', 'pass');

        $dbh->setAttribute(PDO::ATTR_EMULATE_PREPARES, false); 
        $dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

        $this->dbh = $dbh;

      } catch (Exception $e) { //connection failed

        die("Oh no! It seems we took too long to respond");

      }

    }

    public function getLoginInfo() { 

      $sth = $this->dbh->prepare('SELECT pword, loggedin, points FROM login WHERE uname = :uname'); 
      $sth->bindParam(':uname', $username, PDO::PARAM_STR); 

      //cont the code

    }

}

Not sure if it's good enough..but it will work..

来源：https://stackoverflow.com/questions/18321504/php-select-with-pdo-call-to-a-member-function-prepare-on-a-non-object-error