Why Does `mysqli_stmt::num_rows` Consistently Return Zero After Using `prepare`, `bind_param`, `bind_result`, and `fetch`?

mysqli num_rows Consistently Returns Zero

Question:

When using MySQLi's prepare, bind_param, num_rows, bind_result, and fetch methods to retrieve rows from a database, why does num_rows always return 0?

Answer:

Incorrect usage of MySQLi calls. To resolve this issue, execute the following steps prior to fetching the number of rows:

$stmt->execute();
$stmt->store_result();

The call to store_result() is essential for mysqli_stmt::num_rows to work correctly.

Here is a revised code snippet with the store_result() call added:

if ($stmt = $mysqli->prepare("SELECT id, title, visible, parent_id FROM content WHERE parent_id = ? ORDER BY page_order ASC;")) {
    $stmt->bind_param('s', $data->id);
    $stmt->execute();
    $stmt->store_result();
    $num_of_rows = $stmt->num_rows;
    $stmt->bind_result($child_id, $child_title, $child_visible, $child_parent);

    while ($stmt->fetch()) {
        // Code here
    }

    echo($num_of_rows);

    $stmt->close();
}

Please refer to the official documentation for mysqli_stmt::num_rows for further details.

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