Question

One of the patterns that I frequently run across when developing is trying to collect a column/attribute value from a collection of objects into an array. For example:

$ids = array();
foreach ($documents as $document) {
    $ids[] =  $document->name;
}

Am I the only one who runs into this? And does PHP have a way to solve this in fewer lines? I’ve looked but found nothing.

Since I use an MVC framework I have access to a BaseUtil class which contains common functions that don’t really fit in any specific classes. One solution proposed by a co-worker is:

class BaseUtil
{
    public static function collect($collection, $property) {
        $values = array();
        foreach ($collection as $item) {
            $values[] = $item->{$property};
        }
        return $values;
    }
}

Then I can just do:

$ids = BaseUtil::collect($documents, 'name');

Not too shabby. Anyone else have any other ideas? And am I crazy or does this seem like a problem that PHP should have solved a long time ago?

Answer 1

You can use array_map() function for this purpose:

function getName($obj) {
    return $obj->name;
}

$documentsName = array_map("getName", $documents);

You might also consider the create_function() function for lambda functions if you don’t want to create a getName() function in the global namespace.

In PHP 5.3 you might even do:

$documentsName = array_map(function ($obj) { return $obj->name; }, $documents);