Resetting array pointer in PDO results

Question

I'm having trouble moving from MySQL SELECT methods to PDO methods. I want to iterate through a fetched array twice, both times starting with row zero. In MySQL I would use:

mysql_data_seek($result,0);

Using PDO methods, I'm not sure how to accomplish the same thing. The code below is how I am trying to do this. The first while loop works fine but the second while loop returns nothing.

$pdo = new PDO('mysql:host=' . $host . ';dbname='.$database, $username, $password);
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

$stmt = $pdo->prepare('SELECT * FROM mytable WHERE active = 1 ORDER BY name ASC');
$stmt->setFetchMode(PDO::FETCH_ASSOC);
$stmt->execute();

while($row = $stmt->fetch())
{
    //do something starting with row[0]
}
while($row = $stmt->fetch())
{
    //do something else starting with row[0]
}

Answer 1

Save your results to an array and then loop that array twice.

$pdo = new PDO('mysql:host=' . $host . ';dbname='.$database, $username, $password);
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

$stmt = $pdo->prepare('SELECT * FROM mytable WHERE active = 1 ORDER BY name ASC');
$stmt->setFetchMode(PDO::FETCH_ASSOC);
$stmt->execute();

$rows = $stmt->fetchAll();

foreach ($rows as $r) {
    // first run
}

foreach ($rows as $r) {
    // seconds run
}

Answer 2

According too the php manual, you can issue a query multiple times,if you prepare a PDOStatement object using PDO::prepare(), you can issue the statement with multiple calls to PDOStatement::execute(). So your code will look like that.

$stmt = $pdo->prepare('SELECT * FROM mytable WHERE active = 1 ORDER BY name ASC');
$stmt->setFetchMode(PDO::FETCH_ASSOC);

//First execute
$stmt->execute();
while($row = $stmt->fetch())
{
    //do something starting with row[0]
}

//Second execute
$stmt->execute();
while($row = $stmt->fetch())
{
    //do something else starting with row[0]
}

source: http://php.net/manual/en/pdo.query.php

Answer 3

fetch — Fetches the next row from a result set

so when it exits the first while it already arrived to the last element of your resultSet that's why the second while returns nothing .

use fetchAll to store all of your results then go through them .

Answer 4

sometimes storing the result of fetchAll() is not an option. Instead you can just clone the pdo object before calling fetchAll() like this.

$pdo_copy = clone $pdo;

$num_rows = count($pdo_copy->fetchAll());

Now I can still use the pdo object to do statements like fetchObject();