Group rows of a 2d arrays by a column value and push whole rows into subarrays

I have an uploads array that looks like this:

$uploads[0] = array('type' => 'upload', 'label' => 'blah');
$uploads[1] = array('type' => 'upload', 'label' => 'blah');
$uploads[2] = array('type' => 'upload', 'label' => 'blah');
$uploads[3] = array('type' => 'upload', 'label' => 'foobar');

I want to create this array:

$upload_fields = array(
   'blah' => array(
               array('type' => 'upload', 'label' => 'blah')
               array('type' => 'upload', 'label' => 'blah')
               array('type' => 'upload', 'label' => 'blah')
    ),
   'foobar' => array(
               array('type' => 'upload', 'label' => 'foobar')    
    )
);

Basically I want to group the arrays based on their labels. The arrays to be grouped are dynamic otherwise I could do something like:

$array_group_1 = array();
$array_group_2 = array();

foreach($uploads as $upload) {
    if($upload['label'] == 'blah') {
        array_push($array_group_1, $upload);
    }  else {
        array_push($array_group_2, $upload);        
    }
}

$upload_fields = array(
    'blah' => $array_group_1,
    'foobar' => $array_group_2
);

But since the keys are dynamic how can I achieve this?

This is what I came up with:

$uploads[0] = array('type' => 'upload', 'label' => 'blah');
$uploads[1] = array('type' => 'upload', 'label' => 'blah');
$uploads[2] = array('type' => 'upload', 'label' => 'blah');
$uploads[3] = array('type' => 'upload', 'label' => 'foobar');

foreach($uploads as $u){
    $upload_fields[$u['label']][] = $u;
}

echo '<pre>',print_r($upload_fields),'</pre>';