Error in mysqli->prepare with insert statement - php

Question

I'm trying to figure out why my first prepare statement works just fine but my second one doesn't. The actual INSERT INTO syntax looks correct and works when I substitute numbers and place it in a mysql console, but the prepare statement returns false.
Just to clear away the simple questions; $db_table_prefix == "uc_" and all variables are initialized. Also, the first statement sets $results == 0 (EDIT: this was my mistake, it's really 0, not 1).
global $mysqli,$db_table_prefix;
$stmt = $mysqli->prepare("SELECT COUNT(id) FROM ".$db_table_prefix."attempts WHERE ((exp_m = ?) AND (exp_n = ?) AND (max_base <= ?))");
$stmt->bind_param("iii", $m, $n, $this->max_base);
$stmt->execute();
$stmt->bind_result($results);
$stmt->fetch();
if ($results < 1)
{
$stmt = $mysqli->prepare("INSERT INTO ".$db_table_prefix."attempts (exp_m, exp_n, base_x, max_base) VALUES (?,?,?,?)");
$stmt->bind_param("iiii", $m, $n, $x, $this->max_base);
.....
}
I've included the table structure, just in case that's the issue.
mysql> describe uc_attempts;
+----------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+---------------------+------+-----+---------+----------------+
| exp_m | bigint(20) unsigned | NO | | NULL | |
| exp_n | bigint(20) unsigned | NO | | NULL | |
| base_x | bigint(20) unsigned | YES | | NULL | |
| max_base | bigint(20) unsigned | NO | | NULL | |
| id | int(11) | NO | PRI | NULL | auto_increment |
+----------+---------------------+------+-----+---------+----------------+
I'm sure I'm just missing something simple, but after a few days of staring at the code, I needed to ask. Thanks in advance for the help. Please let me know if there is any other information I should include.

Answer 1

You forgot to close the first resource. I believe it can't open a second prepared statement if the first one isn't closed. I think $mysqli->prepare( ... ); will then return false and obviously false->bind_param( ... ); does not exist ;-) causing your Fatal error: Call to a member function bind_param() on a non-object-error.
global $mysqli,$db_table_prefix;
$stmt = $mysqli->prepare("SELECT COUNT(id) FROM ".$db_table_prefix."attempts WHERE ((exp_m = ?) AND (exp_n = ?) AND (max_base <= ?))");
$stmt->bind_param("iii", $m, $n, $this->max_base);
$stmt->execute();
$stmt->bind_result($results);
$stmt->fetch();
$stmt->close(); //<-- this is the problem
if ($results < 1)
{
$stmt = $mysqli->prepare("INSERT INTO ".$db_table_prefix."attempts (exp_m, exp_n, base_x, max_base) VALUES (?,?,?,?)");
$stmt->bind_param("iiii", $m, $n, $x, $this->max_base);
.....
}