PHP UPDATE prepared statement

Question

I\'m trying to learn the proper way to use prepared statements to avoid SQL injections etc.

When I execute the script I get a message from my script saying 0 Rows I

Answer 1

$stmt = $this->mysqli->prepare("UPDATE datadump SET content=? WHERE id=?");
/* BK: always check whether the prepare() succeeded */
if ($stmt === false) {
  trigger_error($this->mysqli->error, E_USER_ERROR);
  return;
}
$id = 1;
/* Bind our params */
/* BK: variables must be bound in the same order as the params in your SQL.
 * Some people prefer PDO because it supports named parameter. */
$stmt->bind_param('si', $content, $id);

/* Set our params */
/* BK: No need to use escaping when using parameters, in fact, you must not, 
 * because you'll get literal '\' characters in your content. */
$content = $_POST['content'] ?: '';

/* Execute the prepared Statement */
$status = $stmt->execute();
/* BK: always check whether the execute() succeeded */
if ($status === false) {
  trigger_error($stmt->error, E_USER_ERROR);
}
printf("%d Row inserted.\n", $stmt->affected_rows);

Re your questions:

I get a message from my script saying 0 Rows Inserted

This is because you reversed the order of parameters when you bound them. So you're searching the id column for the numeric value of your $content, which is probably interpreted as 0. So the UPDATE's WHERE clause matches zero rows.

do I need to declare all the fields or is it ok to just update one field??

It's okay to set just one column in an UPDATE statement. Other columns will not be changed.