我在mysqli中收到错误和警告

Question

UPDATE:

I have a couple of errors and warnings I need help with in mysqli:

Fatal error: Call to undefined method mysqli_stmt::get_result() in ... on line 63

In my code below does anyone know how these warnings and errors can be dealt with?

$query = "SELECT * FROM Teacher WHERE TeacherAlias = ?";
// prepare query
$stmt=$mysqli->prepare($query);
// You only need to call bind_param once
$stmt->bind_param("s",$getid);
// execute query
$stmt->execute();  
//get results
$result = $stmt->get_result(); 

$numrows = mysqli_num_rows($result);
if ($numrows == 0){   

       // don't use $mysqli->prepare here
$query = "SELECT * FROM Teacher WHERE TeacherUsername = ?";
// prepare query
$stmt=$mysqli->prepare($query);
// You only need to call bind_param once
$stmt->bind_param("s",$getuser);
// execute query
$stmt->execute(); 

}

Answer 1

You need to retrieve a mysqli_result object first, with something like...

$res = $stmt->get_result();

... then fetch the number of rows from this object (not $stmt):

$numrows = mysqli_num_rows($res);

UPDATE: get_result method is available in PHP 5.3+ only, for the older versions one should use the following approach:

// $stmt preparing code goes here...

$stmt->execute();
$stmt->store_result();
$num_rows = $stmt->num_rows;
doSomethingWith($num_rows);

// processing cycle:
$stmt->bind_result($some_param, $another_param);
while ($stmt->fetch()) {
   doSomethingElseWith($some_param, $another_param);
}
$stmt->free_result();
$stmt->close();

As a sidenote, two recommendations: 1) it'd be probably faster to use a single query here and look for value both in TeacherAlias and TeacherUsername fields simultaneously (with OR operator, like TeacherAlias = ? OR TeacherUsername = ?); 2) it'd be easier to work with explicitly stated columns (SELECT id, TeacherAlias AS alias, TeacherUsername AS username...) instead of just (SELECT *) in your query.