How to Efficiently Convert a Database Result Into an Associative Array Using PDO?

Converting Result Set into an Associative Array Using Key-Value Pairs with PDO

When working with a query that returns key-value pairs, such as:

<code class="sql">SELECT `key`, `value` FROM `settings`;</code>

You may desire an associative array where the keys and values correspond to the returned data. Typically, this is achieved through a process involving:

<code class="php">$settings_flat = $db
    ->query("SELECT `name`, `value` FROM `settings`;")
    ->fetchAll(PDO::FETCH_ASSOC);

$settings   = array();

foreach ($settings_flat as $setting) {
    $settings[$setting['name']] = $setting['value'];
}</code>

While this method is common, it requires multiple iterations and potential performance issues. However, there is an alternative solution available:

<code class="php">$q = $db->query("SELECT `name`, `value` FROM `settings`;");
$r  = $q->fetchAll(PDO::FETCH_KEY_PAIR);</code>

The PDO::FETCH_KEY_PAIR constant allows you to retrieve data as an associative array directly from the query, simplifying the process and potentially improving performance on larger result sets.

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