sorting - Sort object(SimpleXMLElement) php

Question

I'm trying to find a way to sort my array from SimpleXMLElement. I'd like to sort by start time which I can get from event_start_dt. I'd also like to sort by room ID as a separate process. Currently the array is in order by object(SimpleXMLElement) #. Here is the var_dump($array):

    object(SimpleXMLElement)#275 (1) { 
["reservation"]=> array(3) 
    { 
    [0]=> object(SimpleXMLElement)#287 (28) { 
        ["reservation_id"]=> string(7) "8644894" 
        ["event_start_dt"]=> string(25) "2013-12-02T12:00:00-08:00" 
        ["event_end_dt"]=> string(25) "2013-12-02T13:00:00-08:00" 
        ["event_id"]=> string(6) "314147" 
        ["event_name"]=> string(24) "Practice" 
        ["room_id"]=> string(3) "202"
    }
    [1]=> object(SimpleXMLElement)#288 (28) { 
        ["reservation_id"]=> string(7) "8595185" 
        ["event_start_dt"]=> string(25) "2013-12-02T08:00:00-08:00" 
        ["event_end_dt"]=> string(25) "2013-12-02T09:00:00-08:00" 
        ["event_id"]=> string(6) "314005"
        ["event_name"]=> string(24) "Meeting" 
        ["room_id"]=> string(3) "207"
    }
    [2]=> object(SimpleXMLElement)#289 (28) { 
        ["reservation_id"]=> string(7) "8718654" 
        ["event_start_dt"]=> string(25) "2013-12-02T10:00:00-08:00" 
        ["event_end_dt"]=> string(25) "2013-12-02T11:00:00-08:00" 
        ["event_id"]=> string(6) "315811" 
        ["event_name"]=> string(20) "Maintenance" 
        ["room_id"]=> string(3) "202"
    }
} }

I've tried usort and asort but haven't gotten it to work with either method.

usort method:

function sortByTime($a, $b){
    $a = strtotime($array->event_start_dt);
    $b = strtotime($array->event_start_dt);
        if ($a==$b) return 0;
        return ($a < $b) ?-1 : 1;
        }

        usort($arrTimes, 'sortByTime');

        var_dump($arrTimes);

Trying the code below gives me warning: usort() expects parameter 1 to be array, object given.

foreach ($rez->reservation as $value){ 
    $var1 = $value->space_reservation->space_name;
    $var2 = substr($value->event_start_dt,11,5);
}
sort_obj_arr($value,$var1,SORT_DESC);

echo "<pre>SORTED ";
print_r($value);
echo "</pre>";

function sort_obj_arr(& $arr, $sort_field, $sort_direction)
{
    $sort_func = function($obj_1, $obj_2) use ($sort_field, &$sort_direction)
    {
        if ($sort_direction == SORT_ASC) {
            return strnatcasecmp($obj_1->$sort_field, $obj_2->$sort_field);
        } else {
            return strnatcasecmp($obj_2->$sort_field, $obj_1->$sort_field);
        }
    };
    usort($arr, $sort_func);

}

I have an array from my controler but cannot get usort working: I get either: usort() expects parameter 1 to be array, object given or null.

$array = array($this->data);
print_r($array);

array(1) { 
[0]=> object(SimpleXMLElement)#280 (1) { ["reservation"]=> array(3) { 
        [0]=> object(SimpleXMLElement)#287 (28) { 
            ["reservation_id"]=> string(7) "8644894" 
            ["event_start_dt"]=> string(25) "2013-12-02T12:00:00-08:00" 
            ["event_end_dt"]=> string(25) "2013-12-02T13:00:00-08:00" 
            ["event_id"]=> string(6) "314147" 
            ["event_name"]=> string(24) "Practice" 
            ["room_id"]=> string(3) "202"
        }
        [1]=> object(SimpleXMLElement)#288 (28) { 
            ["reservation_id"]=> string(7) "8595185" 
            ["event_start_dt"]=> string(25) "2013-12-02T08:00:00-08:00" 
            ["event_end_dt"]=> string(25) "2013-12-02T09:00:00-08:00" 
            ["event_id"]=> string(6) "314005"
            ["event_name"]=> string(24) "Meeting" 
            ["room_id"]=> string(3) "207"
        }
        [2]=> object(SimpleXMLElement)#289 (28) { 
            ["reservation_id"]=> string(7) "8718654" 
            ["event_start_dt"]=> string(25) "2013-12-02T10:00:00-08:00" 
            ["event_end_dt"]=> string(25) "2013-12-02T11:00:00-08:00" 
            ["event_id"]=> string(6) "315811" 
            ["event_name"]=> string(20) "Maintenance" 
            ["room_id"]=> string(3) "202"
        }
    } }

Request for print_r:

SimpleXMLElement Object
(
    [reservation] => Array(3)
        (
            [0] => SimpleXMLElement Object
                (
                    [reservation_id] => 8604174
                    [event_start_dt] => 2013-12-31T06:00:00-08:00
                    [event_end_dt] => 2013-12-31T08:00:00-08:00
                    [event_id] => 314147
                    [event_name] => Practice
                    [room_id] => 202
                 )
         [1] => SimpleXMLElement Object
                (
                    [reservation_id] => 8604177
                    [event_start_dt] => 2013-12-31T05:00:00-08:00
                    [event_end_dt] => 2013-12-31T06:00:00-08:00
                    [event_id] => 314150
                    [event_name] => Meeting
                    [room_id] => 216
                 )
         [2] => SimpleXMLElement Object
                (
                    [reservation_id] => 8604189
                    [event_start_dt] => 2013-12-31T10:00:00-08:00
                    [event_end_dt] => 2013-12-31T11:00:00-08:00
                    [event_id] => 314150
                    [event_name] => Maintenance
                    [room_id] => 220
                 )
)
)

$arrTimes = xml2array($array->reservation);

var_dump($arrTimes)

array(5) { 
["reservation_id"]=> string(7) "8604175" 
["event_start_dt"]=> string(25) "2014-01-02T06:00:00-08:00" 
["event_end_dt"]=> string(25) "2014-01-02T08:00:00-08:00" 
["event_id"]=> string(6) "314147" 
["event_name"]=> string(24) "Practice" 
}

Answer 1

Use array_multisort

            foreach ($rez->reservation as $value)
            { 
                     $dateTime[] = $value->event_start_dt;
            }

           array_multisort($dateTime,SORT_ASC,SORT_STRING,$rez->reservation);   
           echo "<pre>";
           print_r($rez->reservation);

Check it. this is my code

<?php
        $myarray=array(
                    0 => array
                        (
                            'dateTime' => '2013-12-02T10:00:00-08:00',
                            'chanl1' => '20.10',
                            'chanl2' => '45.4',
                            'chanl3' => '',
                        ),

                    1 => array
                        (
                            'dateTime' => '2013-12-02T11:00:00-08:00',
                            'chanl1' => '20.11',
                            'chanl2' => '45.4',
                            'chanl3' => '',
                        ),
                  2 => array
                        (
                            'dateTime' => '2013-12-02T12:00:00-08:00',
                            'chanl1' => '20.12',
                            'chanl2' => '33.8',
                            'chanl3' => '',
                        ),

                    3 => array
                        (
                            'dateTime' => '2013-12-02T09:00:00-08:00',
                            'chanl1' => '20.9',
                            'chanl2' => '33.9',
                            'chanl3' => ''
                        ));

            foreach($myarray as $c=>$key) {
                    $dateTime[] = $key['dateTime'];                      
            }           


        array_multisort($dateTime,SORT_ASC,SORT_STRING,$myarray);   
        echo "<pre>";
        print_r($myarray);
        ?>

Output is :

Array
(
    [0] => Array
        (
            [dateTime] => 2013-12-02T09:00:00-08:00
            [chanl1] => 20.9
            [chanl2] => 33.9
            [chanl3] => 
        )

    [1] => Array
        (
            [dateTime] => 2013-12-02T10:00:00-08:00
            [chanl1] => 20.10
            [chanl2] => 45.4
            [chanl3] => 
        )

    [2] => Array
        (
            [dateTime] => 2013-12-02T11:00:00-08:00
            [chanl1] => 20.11
            [chanl2] => 45.4
            [chanl3] => 
        )

    [3] => Array
        (
            [dateTime] => 2013-12-02T12:00:00-08:00
            [chanl1] => 20.12
            [chanl2] => 33.8
            [chanl3] => 
        )

)

FIDDLE