Why can't I loop over $q->fetch() twice?

Question

Assume I\'m in need to loop twice with the result I got form PDO prepared statement.

First loop works fine, the next one does not work

The value of var_d

Answer 1

When you loop the row, you empty out the result set. If you want to loop over multiple times, you can use fetchAll(), store that in a variable and loop that where you need using a foreach loop.

$q = $dbconnection->prepare("SELECT * from users WHERE role=?");
$q->execute(array($id)); //Boolean true or false

$res = $q->fetchAll();

foreach ($res as $row) {
    echo "<br/>" .  $row['user_id'] . "--". $row['fname']. "</br>";
}

foreach ($res as $row) {
    echo "<br/>" .  $row['user_id'] . "--". $row['fname']. "</br>";
}

Alternatively, you can execute the query again, but if you do that, you make a double query to the database. So you query twice for the same data, which isn't very efficient.

Also you had execute(array('$id')), which would be the exact string $id, and not the variable representation. See the PHP manual on strings. So it should be execute(array($id)) instead.

• PHP.net on PDOStatement::fetchAll()

Answer 2

Your are fecth a row time by time if you need two iteration you should perform a copy eg storing rows

  while ($row = $q->fetch(PDO::FETCH_ASSOC)){
      echo "<br/>" .  $row['user_id'] . "--". $row['fname']. "</br>";
      $my_rows[] = $row;
  }



   // second loop  this loop will NOT echo any thing ?!
  foreach($my_rows as $key=>$value){
            echo "<br/>" .  $value['user_id'] . "--". $value['fname']. "</br>";
  }