PDO can I reuse the same Statement Handle for multiple queries? - php

Question

I am using PDO to access my data base and am looping using two while loops with fetch at the same time, seen below:
$DBH = new PDO('mysql:host=localhost;dbname=database;charset=utf8',$dblogin,$dbpass);
$sql = 'SELECT * FROM table';
$STH = $DBH->prepare($sql);
$STH->execute();
while ($bm_table = $STH->fetch(PDO::FETCH_ASSOC))
{
// SQL Query
$sql1 = 'QUERY HERE';
$STH1 = $DBH->prepare($sql1);
$STH1->execute();
// Loops through using different handle, but what if I used STH again?
while ($row = $STH1->fetch(PDO::FETCH_ASSOC))
{
SomeFunction($bm_table,$row);
}
}
As you can see above I am using a different statement handle ($STH, $STH1 etc.) Is this necessary? Or can I use just one statement handle for everything. The reason I have used multiple handles is as the $bm_table value that uses $STH, will still be in use while I am fetching $row wouldn't that change the value of $bm_table or stop the fetch from working? How does the handles with PDO work? Especially when in this case I have two simultaneous fetch loops running at the same time using the same PDO connection.
So the main thing I am looking for here is if I have two statements that are running simultaneously is it important that I use different handles when I continue to use the same connection?

Answer 1

$STH and STH1 are not statement handles, they're just PHP variables. You can reassign a variable if you no longer need its old value. But in the case of this code, you still need the old value.
If you assign $STH inside the outer loop to the handle returned by the second prepare() call, then when it gets back to the top of the loop and re-executes the $STH->fetch() test, it will try to fetch from the second query, not the first one. This will immediately end the outer loop because all those rows have been read.
You can reuse a statement handle for repetitions of the same query. This is very useful when the query has parameters:
$stmt = $DBH->prepare("SELECT * FROM tablename WHERE id = :id");
$stmt->bindParam(':id', $id);
foreach ($id_array as $id) {
$stmt->execute();
$row = $stmt->fetch();
// do stuff with $row
}

Answer 2

If I understand you correctly what you want is dynamic query?... just put a parameter on your method then...
something like this. call it as much as you want with difference parameters though.
Class SampleClass{
public function GetAll($tablename)
{
$sth = $this->prepare("SELECT * FROM $tablename");
$sth->execute();
return $sth->fetchAll();
}
}