Why do I get this function call error on an non-object when I am calling a function on an object?

Question

Error:

Fatal error: Call to a member function bind_param() on a non-object in /var/www/web55/web/pdftest/events.php on line 76

Code:

public function countDaysWithoutEvents(){       
    $sql = "SELECT 7 - COUNT(*) AS NumDaysWithoutEvents
            FROM    
            (SELECT d.date 
                FROM cali_events e
                LEFT JOIN cali_dates d
                ON e.event_id = d.event_id
                WHERE YEARWEEK(d.date) = YEARWEEK(CURRENT_DATE())
                AND c.category_id = ?
                GROUP BY DAY(d.date)
            ) AS UniqueDates";

    $stmt = $this->link->prepare($sql);
    $stmt->bind_param('i', $this->locationID);
    $stmt->execute();

    $stmt->bind_result($count);
    $stmt->close();

    return $count;
}

$this->link->prepare($sql) creates a prepared statement for MySQLi.

Why am I getting this error?

Answer 1

AND c.category_id = ? - there is no table alias c in your query.

Besides that try

$stmt = $this->link->prepare($sql);
if (!$stmt) {
  throw new ErrorException($this->link->error, $this->link->errno);
}

if (!$stmt->bind_param('i', $this->locationID) || !$stmt->execute()) {
  throw new ErrorException($stmt->error, $stmt->errno);
}

Answer 2

I think the problem is obviously with the prepare function..

The function is probably failing, in which case $stmt would be FALSE and hence not have the bind_param method as a member.

From the php mysqli manual:
mysqli_prepare() returns a statement object or FALSE if an error occurred.

Check your query! Maybe there is a problem with your SELECT statement. And also check for FALSE before trying to execute any member function on what you think is an object returned by the prepare function.

if($stmt === FALSE)
    die("Prepare failed... ");// Handle Error Here

// Normal flow resumes here
$stmt->bind_param("i","");

EDIT

I would suspect that the statement may be erroring out because of the sub-query:

SELECT d.date 
 FROM cali_events e
 LEFT JOIN cali_dates d
 ON e.event_id = d.event_id
 WHERE YEARWEEK(d.date) = YEARWEEK(CURRENT_DATE())
 AND c.category_id = ?
 GROUP BY DAY(d.date)

Instead, why don't you write your query like this:

public function countDaysWithoutEvents()
{
    $count = FALSE;

    $sql  = "SELECT COUNT(d.date) ";
    $sql .= " FROM cali_events e ";
    $sql .= "      LEFT JOIN cali_dates d ON e.event_id = d.event_id ";
    $sql .= " WHERE YEARWEEK(d.date) = YEARWEEK(CURRENT_DATE()) ";
    $sql .= "       AND c.category_id = ? ";
    $sql .= " GROUP BY DAY(d.date) ";

    $stmt = $this->link->prepare($sql);
    if($stmt !== FALSE)
    {                
        $stmt->bind_param('i', $this->locationID);
        $stmt->execute();
        $stmt->bind_result($count);
        $stmt->fetch();                    // I think you need to do a fetch
                                           // here to get the result data..
        $stmt->close();
    }else                                  // Or, provide your own error
        die("Error preparing Statement");  // handling here

    return (7 - $count);
}

P.S. I think you also had a missing a call to fetch as well.. (see example above)

Answer 3

$this->link->prepare this statement is not returning the object so it is giving you the error