SELECT in PHP only returns from the second INSERT of the same user

Question

The result of the following SELECT

    <?php
         include_once("conect.php");
         $id = filter_input(INPUT_GET, 'id', FILTER_SANITIZE_STRING);
         $result_usuario = "SELECT * FROM produ_usu WHERE id = '$id'";
         $resultado_usuario = mysqli_query($conn, $result_usuario);
         $row_usuario = mysqli_fetch_assoc($resultado_usuario);

          if(($resultado_usuario) AND ($resultado_usuario->num_rows != 0)){
               while($row_usuario = mysqli_fetch_assoc($resultado_usuario)){
     ?>

only returns data from the second INSERT with same id (user id).

I know the trouble is caused by the line

$row_usuario = mysqli_fetch_assoc($resultado_usuario);

just below the line

$resultado_usuario = mysqli_query($conn, $result_usuario);

Comment the line and SELECT returns after a user’s first INSERT with his id normally.

In short, I do not understand why with the infamous line only returns from the second insert

The question is: why does this line return only after the second Insert of the same id?

Answer 1

The mysqli uses a cursor to control the items you recover through mysqli_fetch_assoc that advances 1 item every time it is called, and as you have already given one mysqli_fetch_assoc there in $row_usuario = mysqli_fetch_assoc($resultado_usuario); , your while is starting on the next item.

This is best explained in php doc https://www.php.net/manual/en/mysqli-result.fetch-assoc.php