How to get all values out of the prepared statement query result - php

Question

I have next code, to create mysqli object and to prepare query:
$GLOBALS['DB_something'] = new mysqli('$database_hostname','$database_username','$database_password','$database_default');
$GLOBALS['DB_prepared_get'] = $GLOBALS['DB_something']->prepare("SELECT ? from database_name WHERE hash=?");
and next code, to get and display the results. Since I haven't been into prepared statements recently, specialy not with PHP, im not sure how to get the results out of it.
When i wrote the code without prepared statements, it works, but for many reasons, I need to rewrite it with prepared statements.
$GLOBALS['DB_prepared_get']->bind_param('ss', $arg, $index);
$GLOBALS['DB_prepared_get']->execute();
$GLOBALS['DB_prepared_get']->bind_result($result); # this is an array of values
$GLOBALS['DB_prepared_get']->fetch();
# below this, I don't know if it's ok
if(mysql_num_rows($result) == 0){
return "0";
}
else{
while($GLOBALS['DB_prepared_get']->fetch()) {
return $result;
}
}
$GLOBALS['DB_prepared_get']->close();
Thanks for any help.
EDIT: just to be clear, my problem is how to fetch the exact result values to print them out or something. So syntax is what I am probably doing wrong.

Answer 1

As far as I know you can't specify the columns of a query as a parameter. You would have to write the columns directly in the prepared statement string.
Something like
$GLOBALS['DB_prepared_get'] = $GLOBALS['DB_something']->prepare("SELECT a,b,c from database_name WHERE hash=?");

Answer 2

There are so many faults in your code that I not even try to explain whats wrong with it. I can say however, that if you are not experienced in OO programming, you first should try to write the procedural code with mysqli.
This code should work:
$mysqli = new mysqli( $database_hostname, $database_username, $database_password, $database_default );
if ($mysqli->connect_error) {
die('Connect Error (' . $mysqli->connect_errno . ') ' . $mysqli->connect_error);
if ($stmt = $mysqli->prepare("SELECT ? from database_name WHERE hash=?")) {
$stmt->bind_param("s", $fieldname); // first marker
$stmt->bind_param("s", $hashwhere); // second marker
$stmt->execute();
$result = array();
while ($stmt->fetch()) {
$result[] = array($fieldname);
}
$stmt->close();
}
$mysqli->close();
var_dump($result);