Add to associative array — but no duplicates

Question

My goal is to append a new set of product records to an existing associative array, but ensure each product is represented only once. I wrote the function below. It looks like way too much code for something this simple. Is there a PHP array function I need to learn about?

function _append ( &$already, $addition ) {
    while( $result = mysql_fetch_array( $addition ) ) {
        $already_found = FALSE;
        foreach ( $already as $try ) {
            if ( $try["products_id"] == $result["products_id"] ) {
                $already_found = TRUE;
                break;
            }
        }
        if ( !$already_found ) { $already[] = $result; }
    }
}

Answer 1

Use the product ID as the key, like $already[$result['products_id']] = $result; , and then you can use array_key_exists to check the product ID easily against all the existing products. (Or, don't. Either way, you'll only have one product per ID; if you don't check, the latest duplicate will overwrite earlier ones.)

Either way, you get rid of the foreach altogether.

function _append(&$already, $addition) {
    while ($result = mysql_fetch_array($addition)) {
        if (!array_key_exists($result['products_id'], $already)) {
            $already[$result['products_id']] = $result;
        }
    }
}

The catch is, your array is no longer numerically indexed. Wherever you add items to it, you add them with their key (the value of products_id). But you can say foreach ($items as $item) just like always.

Answer 2

How about assigning the product id as the array key in $already ?

while( $result = mysql_fetch_array( $addition ) ) {
  $already[$result['products_id']] = $result;
}

This will of course overwrite the old product record, but it should gracefully avoid duplicates!