数组自定义排序？该如何处理

<br />Array<br />(<br />    [ban] => Array<br />        (<br />            [0] => Array<br />                (<br />                    [id] => 1<br />                    [uid] => 1<br />                    [username] => admin                 <br />                    [posttime] => 2014-07-19 11:54<br />                )<br />        )<br /> <br />    [ale] => Array<br />        (<br />            [0] => Array<br />                (<br />                    [id] => 2<br />                    [uid] => 1<br />                    [username] => admin<br />                    [posttime] => 2014-07-19 12:02<br />                ) <br />        )<br />	[text] => Array<br />        (<br />            [0] => Array<br />                (<br />                    [id] => 5<br />                    [uid] => 1<br />                    [username] => admin<br />                    [posttime] => 2014-07-19 12:02<br />                ) <br />        )<br />)<br />