what are prepared statements in php code example

Example 1: php prepared statement select

// Multiple rows:
$sql = "SELECT * FROM users WHERE id=?";
$stmt = $conn->prepare($sql); 
$stmt->bind_param("i", $id);
$stmt->execute();
$result = $stmt->get_result();
while ($row = $result->fetch_assoc()) {
    echo $row['name'];
}

//Single row:
$sql = "SELECT user FROM users WHERE id=?"; // SQL with parameters
$stmt = $conn->prepare($sql); 
$stmt->bind_param("i", $id);
$stmt->execute();
$result = $stmt->get_result(); // get the mysqli result
$user = $result->fetch_assoc(); // fetch data  

// Update/delete from
$sql = "UPDATE users SET rank=?, status=? WHERE id=?"; // SQL with parameters
$sql = "DELETE FROM users WHERE id=?";
$stmt = $conn->prepare($sql);

$stmt->bind_param('sss', $rank, $status, $id);
$stmt->execute();

Example 2: php mysql prepare query

$stmt = $mysqli->prepare("SELECT * FROM myTable WHERE name = ? AND age = ?");
$stmt->bind_param("si", $_POST['name'], $_POST['age']);
$stmt->execute();
$stmt->close();