Array sorting in php

We have an array and need to sort the above array

Array
(
    [0] => stdClass Object
        (
            [id] => 229
            [firstname] => ggg
            [lastname] => fff
        )

    [1] => stdClass Object
        (
            [id] => 230
            [firstname] => aaa
            [lastname] => jjj
        )

)

I want to sort the array as (Sort by firstname)

Array
(
    [0] => stdClass Objec开发者_StackOverflow中文版t
        (
            [id] => 230 
            [firstname] => aaa
            [lastname] => jjj

        )

    [1] => stdClass Object
        (
            [id] => 229
            [name] => ggg
            [lastname] => fff
        )

)

Use usort:

usort($ar, function($a, $b) {
  return strcmp($a->firstname, $b->firstname);
});