How do I reuse a PDOStatement prepare? - php

Question

I made a search but I couldn't find anything fulfilling
Imagine the following:
<?php
$connection = new \PDO($dsn, $user, $pass);
$stmt1 = $connection->prepare("
SELECT
*
FROM
table
WHERE
a = :a
AND b = :b
AND c = :c
AND d = :d
AND search LIKE :search
");
$stmt1->bindValue(":a", $a);
$stmt1->bindValue(":b", $b);
$stmt1->bindValue(":c", $c);
$stmt1->bindValue(":d", $d);
$stmt2 = clone $stmt1;
$stmt1->bindValue(":search", "a%");
$stmt2->bindValue(":search", "b%");
$stmt1->execute();
$stmt2->execute();
while(($r1 = $stmt1->fetchObject()) && ($r2 = $stmt2->fetchObject()))
echo $r1->foo . " " . $r2->foo . "\n";
}
Am I allowed to do something like this? How can I clone/reuse a PDOStatement instance and use it at the same time of its original instance?
Don't say "use UNION", that's not the point of my question :P
Thank you in advance.

Answer 1

This is not what prepared statement re-use is for. The idea of reusing a prepared statements is consecutive, not concurrent.
So you can do this:
$connection = new \PDO($dsn, $user, $pass);
$stmt = $connection->prepare("
SELECT *
FROM table
WHERE a = :a
AND b = :b
AND c = :c
AND d = :d
AND search LIKE :search
");
$stmt->bindValue(":a", $a);
$stmt->bindValue(":b", $b);
$stmt->bindValue(":c", $c);
$stmt->bindValue(":d", $d);
foreach (["a%", "b%"] as $search) {
$stmt->bindValue(":search", $search);
$stmt->execute();
while($r = $stmt->fetchObject()) {
echo $r->foo . "\n";
}
$stmt->closeCursor();
}
If you want to handle multiple result sets concurrently (at least with MySQL), you will need to do one of the following:
Use an appropriate set of UNION/JOIN to create a single result set.
Buffer the result sets in memory and iterate them again when you have all the data available.
Create multiple connections - you cannot have more than one open statement cursor per connection, but you can have multiple open connections.
If you want to use multiple connections, your code becomes:
$query = "
SELECT *
FROM table
WHERE a = :a
AND b = :b
AND c = :c
AND d = :d
AND search LIKE :search
";
$connection1 = new \PDO($dsn, $user, $pass);
$connection2 = new \PDO($dsn, $user, $pass);
$stmt1 = $connection1->prepare($query);
$stmt1->bindValue(":a", $a);
$stmt1->bindValue(":b", $b);
$stmt1->bindValue(":c", $c);
$stmt1->bindValue(":d", $d);
$stmt1->bindValue(":search", "a%");
$stmt2 = $connection2->prepare($query);
$stmt2->bindValue(":a", $a);
$stmt2->bindValue(":b", $b);
$stmt2->bindValue(":c", $c);
$stmt2->bindValue(":d", $d);
$stmt2->bindValue(":search", "b%");
$stmt1->execute();
$stmt2->execute();
while(($r1 = $stmt1->fetchObject()) && ($r2 = $stmt2->fetchObject()))
echo $r1->foo . " " . $r2->foo . "\n";
}
$stmt1->closeCursor();
$stmt2->closeCursor();

Answer 2

Sounds like you're looking for an abstraction of a prepared statement that is able to carry it's own parameters with it.
As you actually consume each result by traversing it, adding an Iterator that knows how to traverse such a parametrized prepared statement looks fitting then.
However this suggestion is not part of PDO, so you would need to write it your own (however this might also prevent to repeat yourself with PDO code and you perhaps can even deffer the actual creation and execution of the statement so this might also create some benefit for lazy loading data).