親の配列を子の値で並べ替え

Question

どのようにして、下の配列を子の値（つまり、post_id、usernameなど）で並べ替えることができますか？

Array(
[0] => Array 
    (
     [id] => 10 
     [post_id] => 398 
     [user_id] => 0 
     [view_date] => 2010-11-20 15:26:00 
     [views] => 4 
     [username] => <em>guest</em> 
    ) 

[1] => Array 
    (
     [id] => 9 
     [post_id] => 397 
     [user_id] => 1 
     [view_date] => 2010-11-19 23:35:39 
     [views] => 1 
     [username] => Fire G 
    ) 

[2] => Array 
    (
     [id] => 8 
     [post_id] => 398 
     [user_id] => 1 
     [view_date] => 2010-11-19 23:35:26 
     [views] => 4 
     [username] => Fire G 
    ) 

[3] => Array 
    (
     [id] => 7 
     [post_id] => 396 
     [user_id] => 1 
     [view_date] => 2010-11-19 23:07:57 
     [views] => 3 
     [username] => Fire G 
    ) 

[4] => Array 
    (
     [id] => 6 
     [post_id] => 396 
     [user_id] => 1 
     [view_date] => 2010-11-19 23:07:55 
     [views] => 3 
     [username] => Fire G 
    ) 

[5] => Array 
    (
     [id] => 5 
     [post_id] => 396 
     [user_id] => 1 
     [view_date] => 2010-11-19 23:07:52 
     [views] => 3 
     [username] => Fire G 
    ) 

[6] => Array 
    (
     [id] => 4 
     [post_id] => 13 
     [user_id] => 1 
     [view_date] => 2010-11-19 22:59:35 
     [views] => 1 
     [username] => Fire G 
    ) 

[7] => Array 
    (
     [id] => 3 
     [post_id] => 3 
     [user_id] => 1 
     [view_date] => 2010-11-19 22:59:28 
     [views] => 1 
     [username] => Fire G 
    ) 

[8] => Array 
    (
     [id] => 2 
     [post_id] => 398 
     [user_id] => 1 
     [view_date] => 2010-11-18 11:37:20 
     [views] => 4 
     [username] => Fire G 
    ) 

[9] => Array 
    (
     [id] => 1 
     [post_id] => 398 
     [user_id] => 1 
     [view_date] => 2010-11-18 11:37:16 
     [views] => 4 
     [username] => Fire G 
    ) 
) 

Answer 1

使用uasort、あなたは一つの要素が他の前に来る必要があるかどうかを定義する独自の機能を提供することができますユーザ定義のソート。

http://www.php.net/manual/en/function.uasort.php

あなたのコンパレータ機能は

function cmp($a, $b) { 
    return $a['post_id'] > $b['post_id'] ? 1 : -1; 
}