->num_rows doesn't work correctly [duplicate] - php

Question

This question already has answers here:
PHP MYSQLI number of rows doesnt work no errors
(3 answers)
Closed 6 years ago.
I don't understand why $amountOfUsers is showing as 0?
This used to work before I moved to the bind_param function... I was only using query() instad of prepare. But this is a lot safer, I just have trouble understand why this doesn't work, and how to fix it.
$stmt = $mysqli->prepare("SELECT id, expire, status, username FROM username WHERE username= ?");
$stmt->bind_param('s', $username);
$stmt->execute();
//Counting results. 0 = Invalid, 1 = Valid
$amountOfUsers = $stmt->num_rows;
The error I am getting is: $amountOfUsers isn't counting the number of results properly.

Answer 1

$stmt = $mysqli->prepare("SELECT id, expire, status, username FROM username WHERE username= ?");
$stmt->bind_param('s', $username);
$stmt->execute();
// Store the result (so you can get the properties, like num_rows)
$stmt->store_result();
// Get the number of rows
$amountOfRows = $stmt->num_rows;
// Bind the result to variables
$stmt->bind_result($id, $expire, $status, $db_username);
// Process the variables
while($stmt->fetch()) {
printf("%d %s %s %s\n", $id, $expire, $status, $db_username);
}

Answer 2

Sometimes things don't go according to plan. Checking result codes and errors available in your library is usually more efficient for troubleshooting than asking strangers, but hopefully this stranger can help... choose one of these patterns:
A:
$result = $stmt->execute();
if (!$result) { /* handle errors */ }
B:
$stmt->execute();
if ($stmt->errno != 0) { /* handle errors */ }
C (for development troubleshooting only, not code you would leave around):
$stmt->execute();
print_r($stmt->error_list);
More info here and associated pages:
http://www.php.net/manual/en/mysqli-stmt.errno.php

Answer 3

I would never in my life understand why php users are so inclined to the number of rows returned.
Especially if used only as a flag... if any data returned!
Why not to take the very returned data and see?
$sql ="SELECT id, expire, status, username FROM username WHERE username= ?s";
$stmt = $mysqli->prepare($sql);
$stmt->bind_param('s', $username);
$stmt->execute();
$res = $stmt->get_result();
$row = $res->fetch_assoc();
if ($row)
{
// do whatever
}
I would never understand an inclination to long and windy codes as well.
Why not to get yourself an abstraction library and get everything in one single line?
$sql = "SELECT id, expire, status, username FROM username WHERE username= ?";
if ($row = $db->getRow($sql))
{
// do whatever
}