PDO Dynamic Query Building - php

Question

I have been old school using mysql_query and starting out now using PDO. Which is great!
But in my old scripts I had build a dynamic query builder, and i'm having a tough time porting that over using PDO.
If anyone can give me some direction that would be great!
Here is the theory of it.
I have an array of
the DB Fields and Values (upon insert).
Create the query string to product a valid PDO transaction
Here is a portion of what i'm trying to do.
public $dbFields; // This is an array of the fields plus VALUES
public function select($where, $limit) {
// This is what I **had** before
$query = "SELECT ". implode(", ", $this->dbFields) ." FROM ". $this->table." WHERE ". $where ." ". $limit."";
// Now i need to convert that to PDO
$this->connection->beginTransaction();
# START Query
$select = $this->connection->prepare("SELECT {$this->fieldNames} FROM {$this->table}");
// I need to BIND my params and values, but i'm not sure the best route to take when I have a WHERE clause that includes, "AND" / "OR" operators.
# EXECUTE the query
$select->execute();
$this->connection->commit();
}
This is what I HAD before
$results = $db->select("userId = 111 OR userId = 222");
But what i'm thinking I need to do is use something more like
$results = $db->select(array("userId"=>111, "userId"=>222));
I know this is a tall order, and I hope it makes sense in what i'm trying to do, but any help in trying to build these queries would be greatly appreciated.

Answer 1

You'll need a separate $params parameter to your select method. I took the liberty of providing defaults for the method parameters. Like #userXxxx notes, you don't need a transaction just to do a SELECT.
<?php
class db {
public $connection; //PDO
public $dbFields; // This is an array of the fields plus VALUES
public function select($where = '1', $params = array(), $limit = '', $fetchStyle = PDO::FETCH_ASSOC) { //fetchArgs, etc
$fields = implode(', ', $this->dbFields);
//create query
$query = "SELECT $fields FROM {$this->table} WHERE $where $limit";
//prepare statement
$stmt = $this->connection->query($query);
$stmt->execute($params);
return $stmt->fetchAll($fetchStyle);
}
//...
}
$where = 'userId IN(:userId1, :userId2)';
$params = array(':userId1' => 111, ':userId2' => 2222);
$db->select($where, $params);
Notes:
If you really want, you can add additional method parameters to match up with all the flexibility of PDOStatement::fetchAll.
I'm not sure what you mean about $dbFields being "fields plus VALUES". Can you explain?
[Edit]
You might want to take a look at the docs/examples for PDOStatement::execute, since that seemed to be where your confusion was rooted--in particular, the $input_parameters method parameter.

Answer 2

What about this?
public function select($where, $limit) {
$query = "SELECT ". implode(", ", $this->dbFields) ." FROM ". $this->table." WHERE ". $where ." ". $limit."";
$this->connection->query($query);
}
//Use what you had before:
$results = $db->select("userId = 111 OR userId = 222");
Not sure why you want to use transaction (for all-or-nothing basis or catching exceptions and rollback) or prepared queries (for sending multiple queries)...