Sort strings that also contain some integers

Question

Using usort(), is it possible to sort strings that also contain integer values?

For example, take this array of objects containing email addresses (and other data) -

$invitees = Array(
    [0] => Array(
        'email' => 'test11@testing.com'
    ),
    [1] => Array(
        'email' => 'test2@testing.com'
    ),
    [2] => Array(
        'email' => 'test1@testing.com'
    )
);

Using the following code compares the array elements as just a simple string -

/** Sort the data (if the sort key is defined) */
if(!empty($_REQUEST['orderby'])) :
    usort($emails, array(&$this, '_order_callback'));
endif;

function _order_callback($item_a, $item_b){

    /** Grab 'orderby', which must have been set for this function to be called */
    $orderby = $_REQUEST['orderby'];

    /** If no 'order' is not set, default to ASC */
    $order = (!empty($_REQUEST['order'])) ? $_REQUEST['order'] : 'ASC';

    $result = strcmp($item_a[$orderby], $item_b[$orderby]);

    return (strtoupper($order) === 'ASC') ? $result : -$result; //Send final sort direction to usort

}

The results are delivered in the following order -

[0] - 'test11@testing.com'
[2] - 'test1@testing.com'
[1] - 'test2@testing.com'

Where as I desire this order -

[2] - 'test1@testing.com'
[1] - 'test2@testing.com'
[0] - 'test11@testing.com'

Is this possible with usort()? Thanks.

---

Edit

Now that I know of the existence of natsort() (thanks to the below comments/answers), I was able to find and try this -

$result = ($item_a[$orderby] > $item_b[$orderby] ? 1 : ($item_a[$orderby] < $item_b[$orderby] ? -1 : 0));

I added that comparison to my _order_callback() function (if $orderby === email), and it's close, but sorts in the order 11, 12, 13, 14, 1, 2, 3, 4.

Answer 1

Use strnatcmp() to do the comparison in your usort() callback

$email1 = new StdClass;
$email1->email = 'test11@testing.com';
$email2 = new StdClass;
$email2->email = 'test1@testing.com';
$email3 = new StdClass;
$email3->email = 'test2@testing.com';
$email4 = new StdClass;
$email4->email = 'test12@testing.com';
$email5 = new StdClass;
$email5->email = 'test21@testing.com';
$email6 = new StdClass;
$email6->email = 'test3@testing.com';

$invitees = array(
    $email1,
    $email2,
    $email3,
    $email4,
    $email5,
    $email6,
);


usort($invitees, '_order_callback');

function _order_callback($item_a, $item_b){
    return strnatcmp($item_a->email, $item_b->email);
}

var_dump($invitees);

Answer 2

As Mark Baker says, natsort is what you are looking for.

$emails = array(
    'test2@testing.com',
    'test11@testing.com',
    'test1@testing.com'
);

natsort( $emails );

Answer 3

Thanks to @MarkBaker, @MajorCaiger and @hdvianna, here is the final order callback function that I am using.

This function takes in to account multiple sort criteria from a multi-dimensional array.

/** Sort the data (if the sort key is defined) */
if(!empty($_REQUEST['orderby'])) :
    usort($invitees[$status], array(&$this, '_order_callback'));
endif;

/**
 * Callback function to order event invitees
 *
function _order_callback($item_a, $item_b){

    /** Grab 'orderby', which must have been set for this function to be called */
    $orderby = $_REQUEST['orderby'];

    /** If no 'order' is not set, default to ASC */
    $order = (!empty($_REQUEST['order'])) ? $_REQUEST['order'] : 'ASC';

    switch($orderby) :

        case 'ID' : // ID is unique, so just sort by ID
            $result = strnatcmp($item_a[$orderby], $item_b[$orderby]);
            break;

        case 'email' :
            $result = strnatcasecmp($item_a[$orderby], $item_b[$orderby]);
            if($result === 0) :
                $result = strcmp($item_a['first_name'], $item_b['first_name']);
            endif;
            if($result === 0) :
                $result = strcmp($item_a['surname'], $item_b['surname']);
            endif;
            break;

        case 'name' :
            $result = strcmp($item_a['first_name'], $item_b['first_name']); // Explicitly declare 'first_name' here as $orderby is actuualy 'name', which is a constructed field for display
            if($result === 0) :
                $result = strcmp($item_a['surname'], $item_b['surname']);
            endif;
            if($result === 0) :
                $result = strnatcasecmp($item_a['email'], $item_b['email']);
            endif;
            break;

        default : // 'custom' and 'town'
            $result = strcmp($item_a[$orderby], $item_b[$orderby]);
            break;

    endswitch;

    return (strtoupper($order) === 'ASC') ? $result : -$result; //Send final sort direction to usort

}