PHP Call to a member function prepare() on a non-o

问题:

Hi i need some help with this error I keep getting. It works fine everywhere else in the script except when I try to call it within this one function.

The function I am calling is: getTotalServers

Error:

Fatal error: Call to a member function prepare() on a non-object in C:\xampp2\htdocs\runeloft\ss_sources\util.php on line 208

Calling in this function:

function display_table($online, $where, $num_servers = null){
global $aaaa, $bbbb;
 $num_per_page = 30;

 $page = 1;

 // how many records per page
 $size = 10;

 // we get the current page from $_GET
 if (isset($_GET['page'])){
     $page = (int) $_GET['page'];
 }

 $aaaa = getTotalServers(1, $num_servers);;
 $bbbb = $page;

 // create the pagination class
 $pagination = new Pagination();
 $pagination->setLink("?action=status&page=%s");
 $pagination->setPage($page);
 $pagination->setSize($size);
 $pagination->setTotalRecords($num_servers);

 global $g_headers;
 $g_headers = array(
           'name' => 'Server Name',
           'ip' => 'IP',
           'port' => 'Port',
           'uptime' => 'Uptime',
           'online' => 'Status',
           );

 $start = isset($_GET['start']) ? $_GET['start'] : 0;

 mysql_con();
 global $g_mysqli;
 $start = $g_mysqli->real_escape_string($start);
 if(isset($_GET['sort']) && isset($g_headers[$_GET['sort']])){
      $order_by = 'ORDER BY `'.$g_mysqli->real_escape_string($_GET['sort']).'` '.(isset($_GET['desc']) ? 'DESC' : 'ASC');
 }else{
      //default sort
      $order_by = 'ORDER BY `uptime` DESC, `time` ASC';
 }

 //$order_by .= " LIMIT $start, $num_per_page";
 $order_by .= " " . $pagination->getLimitSql();

 if($start == 0 && $online == 1 && !isset($_GET['sort']))
      echoTable('Spons', "`sponsored` != '0'", "ORDER BY `sponsored` DESC, RAND() LIMIT 10");



 echoTable('Other', $where, $order_by, $online, $start, $num_per_page, $num_servers);
 close_mysql();
}

Called Function:

function getTotalServers($online, $where, $num_servers = null){
$where = "`online` = '$online' AND `sponsored` = '0'";
 if($num_servers == null){
      global $g_mysqli;
      $stmt = $g_mysqli->prepare("SELECT COUNT(*) FROM `servers` WHERE ".$where) or debug($g_mysqli->error);
      $stmt->execute();
      // bind result variables
      $stmt->bind_result($num_servers);
      $stmt->fetch();
      $stmt->close();
 }
    return $num_servers;

}

Thanks for any help.

回答1:

My guess is that as mysql_con has not been called at that point, the $g_mysql variable does not exist.

If you try to call a method on a non-object, PHP will trigger the error you are seeing. Basically since the variable doesn't exist, it's defaulting to null.

$a = null;
$a->prepare()

Makes no sense, so that's why PHP is throwing that error.

On a different note, you really shouldn't use global variables. You can google or search stackoverflow for a more detailed list, but in short, they break portability of code, and make errors like this one harder to spot. It's a pain to pass an extra parameter to each function call that needs it, but it's much better from a design point of view (and really not much extra effort :p).

回答2:

The object $g_mysqli should be initialized BEFORE it is called in your code.

In your case you are creating global variable $g_mysqli at many places but every time it is a NULL object before you initialize it.

So you can't call any function within null object.

回答3:

The problem is with header() function. The all you need to do is to add a ob_start() at the top of your codes in any page which uses header() function.

Just a confusing error!!! If anyone knows the reason please explain..