How do I loop through a MySQL query via PDO in PHP? - php

Question

I'm slowly moving all of my LAMP websites from mysql_ functions to PDO functions and I've hit my first brick wall. I don't know how to loop through results with a parameter. I am fine with the following:
foreach ($database->query("SELECT * FROM widgets") as $results)
{
echo $results["widget_name"];
}
However if I want to do something like this:
foreach ($database->query("SELECT * FROM widgets WHERE something='something else'") as $results)
{
echo $results["widget_name"];
}
Obviously the 'something else' will be dynamic.

Answer 1

Here is an example for using PDO to connect to a DB, to tell it to throw Exceptions instead of php errors (will help with your debugging), and using parameterised statements instead of substituting dynamic values into the query yourself (highly recommended):
// connect to PDO
$pdo = new PDO("mysql:host=localhost;dbname=test", "user", "password");
// the following tells PDO we want it to throw Exceptions for every error.
// this is far more useful than the default mode of throwing php errors
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
// prepare the statement. the placeholders allow PDO to handle substituting
// the values, which also prevents SQL injection
$stmt = $pdo->prepare("SELECT * FROM product WHERE productTypeId=:productTypeId AND brand=:brand");
// bind the parameters
$stmt->bindValue(":productTypeId", 6);
$stmt->bindValue(":brand", "Slurm");
// initialise an array for the results
$products = array();
$stmt->execute();
while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
$products[] = $row;
}

Answer 2

According to the PHP documentation is says you should be able to to do the following:
$sql = "SELECT * FROM widgets WHERE something='something else'";
foreach ($database->query($sql) as $row) {
echo $row["widget_name"];
}

Answer 3

If you like the foreach syntax, you can use the following class:
// Wrap a PDOStatement to iterate through all result rows. Uses a
// local cache to allow rewinding.
class PDOStatementIterator implements Iterator
{
public
$stmt,
$cache,
$next;
public function __construct($stmt)
{
$this->cache = array();
$this->stmt = $stmt;
}
public function rewind()
{
reset($this->cache);
$this->next();
}
public function valid()
{
return (FALSE !== $this->next);
}
public function current()
{
return $this->next[1];
}
public function key()
{
return $this->next[0];
}
public function next()
{
// Try to get the next element in our data cache.
$this->next = each($this->cache);
// Past the end of the data cache
if (FALSE === $this->next)
{
// Fetch the next row of data
$row = $this->stmt->fetch(PDO::FETCH_ASSOC);
// Fetch successful
if ($row)
{
// Add row to data cache
$this->cache[] = $row;
}
$this->next = each($this->cache);
}
}
}
Then to use it:
foreach(new PDOStatementIterator($stmt) as $col => $val)
{
...
}