PDO Problem -> Call to a member function on a non-object - php

Question

I have been turning and twisting this to the best of my non-existing PDO knowledge, but still without any luck.
the code:
function write($id, $data) {
global $dbcon;
$id = mysql_real_escape_string($id);
$data = mysql_real_escape_string($data);
$sql = $dbcon->exec("INSERT INTO `sessions`
(`session_id`, `session_data`,
`session_expire`, `session_agent`,
`session_ip`, `session_referrer`)
VALUES
(\"".$id."\", \"".$data."\",
\"".time()."\",\"".($this->session_encryption($_SERVER['HTTP_USER_AGENT']))."\",
\"".($this->session_encryption($_SERVER['REMOTE_ADDR']))."\", \"".($this->session_encryption((isset($_SERVER['HTTP_REFERER']) ? $_SERVER['HTTP_REFERER'] : str_shuffle('ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_^~#&|=+;!,(){}[].?%*#'))))."\")
ON DUPLICATE KEY UPDATE
`session_data` = \"".$data."\",
`session_expire` = \"".time()."\"");
return true;
}
Give me the following error:
Fatal error: Call to a member function exec() on a non-object
on the
$sql = $dbcon->exec(
line.
I have been trying to solve this all evening, but without any luck.
This is my PDO connection script:
require_once(INC_PATH.'/config.php');
$dsn = "$db_type:host=$db_host;port=$db_port;dbname=$db_name;charset=$db_charset";
try{
$dbcon = new PDO($dsn, $db_user, $db_pass);
$dbcon->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
//$dbcon = null; //Close database connection.
}
catch(PDOException $e){
echo $e->getMessage();
}
Hope one of you kind souls out there can help me, I would deeply appreciate it!
Thanks.
UPDATE:
I have a global.php file which looks like this:
//Load database
require_once(INC_PATH.'/database.php');
//Load session handler
require_once(INC_PATH.'/class_sessions.php');
$Sessions = new SessionManager();
session_start();
The database.php is included before the sessions class, and when I view the website, it does not give any errors on this part of the sessions class (which is before the write function:
function read($id) {
global $dbcon;
$data = '';
$id = mysql_real_escape_string($id);
$sql = $dbcon->prepare("SELECT
`session_data`
FROM
`sessions`
WHERE
`session_id` = '".$id."'");
$sql->execute();
$a = $sql->columnCount();
if($a > 0) {
$row = $sql->fetchObject();
$data = $row['session_data'];
}
return $data;
}

Answer 1

Are you sure your connection script is getting executed? Try checking if $dbcon is set. Also, you may be missing global $dbcon within the connection script.
By the way, since you're already using PDO, might I recommend you use placeholders in your query:
$sql = "INSERT INTO `sessions`
(`session_id`, `session_data`, `session_expire`,
`session_agent`, `session_ip`, `session_referrer`)
VALUES
(:session_id, :session_data, :session_expire,
:session_agent, :session_ip, :session_referrer)
ON DUPLICATE KEY UPDATE
`session_data` = :session_data,
`session_expire` = :session_expire";
$params = array(
':session_id' => $id,
':session_data' => $data,
':session_expire' => time(),
':session_agent' => $this->session_encryption($_SERVER['HTTP_USER_AGENT']),
':session_ip', => $this->session_encryption($_SERVER['REMOTE_ADDR']),
':session_referrer' => $this->session_encryption((isset($_SERVER['HTTP_REFERER']) ? $_SERVER['HTTP_REFERER'] : str_shuffle('ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_^~#&|=+;!,(){}[].?%*#';
);
$stmt = $dbcon->prepare($sql);
if ($stmt->execute($params) === FALSE) {
// handle error
}

Answer 2

First check that the global object is not being overwritten by another function. I strongly suggest you use Dependency injection instead of globals.
$Sessions = new SessionManager($dbcon);
And inside the Session Management class you can do something like
class SessionManager
{
protected $db;
public function __construct($db) { $this->db = $db; }
public function read($id)
{
$stmt = $this->db->prepare("SELECT session_data
FROM sessions
WHERE session_id = ?");
$stmt->execute(array($id));
return $stmt->fetchColumn();
}
}
And secondly, since you are using PDO, you dont need to call mysql_real_escape_string(), use prepared statements and placeholders :)