php function not returning class object - php

Question

I have a DB class that I've created several functions in to return various values. One of the functions returns (or is supposed to) a "user" class object that represents a logged in user for the application.
class user {
public $guid = '';
public $fname = '';
public $lname = '';
public function __construct() {}
public function print_option() {
return "<option value='$this->guid'>$this->name</option>";
}
}
In the DB class I have the following 2 functions:
public function get_user($uid) {
$sql = '';
$usr = new user();
$sql = "SELECT guid, fname, lname FROM ms.users WHERE guid=?";
if($sth = $this->conn->prepare($sql)) {
$sth->bind_param('s', $uid);
if($sth->execute()) {
$sth->bind_result($usr->guid, $usr->fname, $usr->lname);
$sth->fetch();
print_r($usr); // PRINTS OUT CORRECTLY
return $usr;
}
else {return null;}
}
else {return null;}
}
public function get_practice_user_list($pguid) {
$ret = '';
$sql = "SELECT user_guid FROM ms.perm WHERE p_guid=?";
if($sth = $this->conn->prepare($sql)) {
$sth->bind_param('s', $pguid);
if($sth->execute()) {
$usr = new user();
$guid = '';
$sth->bind_result($guid);
while($sth->fetch()) {
print_r($guid); // PRINTS GUID correctly
$usr = $this->get_user($guid);
print_r($usr); // PRINTS NOTHING object is null so prints "error" two lines later.
if($usr != null) $ret .= $usr->print_option();
else print "error";
}
return $ret;
}
else {return null;}
}
else {return null;}
}
I'm just not understanding why the "user" object is not returning in this instance. Others calls to the get_user function work just fine and return the user class object pertaining to that user.
TIA

Answer 1

I guess you guid may be an integer so
$sth->bind_param('s', $uid);
bind_param's first param should be 'i' not 's';
http://www.php.net/manual/en/mysqli-stmt.bind-param.php

Answer 2

The problem was with the query. Since the code was just looping through one query (get_practice_user_list), then calling the get_user function and attempting a second query MySQL came back with an error of out of sync message. When I looked that up, I was able to fix it by doing a fetch_all on the first query then looping through that array to get the users.