使用匿名函數進行字母排序的比較函數

Question

我有一個二維數組，並且想按名稱排序。我想使用具有匿名功能的usort()。當我想按字母順序排序時，我的比較函數應該如何顯示？

[names] => Array 
(
    [0] => Array 
     (
      [name] => Baba 
      [prename] => Ali 
     ) 

    [1] => Array 
     (
      [name] => Pan 
      [prename] => Peter 
     ) 

) 

排序，我嘗試這樣做：

usort($names, function cmp($a, $b) { 
    return strcmp($a['name'], $b['name']); 
}); 

這給了我unexpected T_STRING, expecting '('第一線。

Answer 1

的錯誤是不那麼明顯，但對匿名函數的概念反覆思考，我得到了暗示。函數名稱不能在那裏。我確切的問題，正確的解決方法是

usort($names, function ($a, $b) { 
    return strcmp($a['name'], $b['name']); 
}); 

Answer 2

可以使用usort

$names = Array(
"0" => Array("name" => "B","prename" => "A"), 
"1" => Array("name" => "D","prename" => "B"), 
"2" => Array("name" => "A","prename" => "C"), 
"3" => Array("name" => "B","prename" => "D") 

     ); 

實施例1

__xsort($names,"name"); 
var_dump($names); 

輸出

array 
    0 => 
    array 
     'name' => string 'A' (length=1) 
     'prename' => string 'C' (length=1) 
    1 => 
    array 
     'name' => string 'B' (length=1) 
     'prename' => string 'A' (length=1) 
    2 => 
    array 
     'name' => string 'B' (length=1) 
     'prename' => string 'D' (length=1) 
    3 => 
    array 
     'name' => string 'D' (length=1) 
     'prename' => string 'B' (length=1) 

實施例2

__xsort($names,"prename"); 
var_dump($names); 

輸出

array 
    0 => 
    array 
     'name' => string 'B' (length=1) 
     'prename' => string 'A' (length=1) 
    1 => 
    array 
     'name' => string 'D' (length=1) 
     'prename' => string 'B' (length=1) 
    2 => 
    array 
     'name' => string 'A' (length=1) 
     'prename' => string 'C' (length=1) 
    3 => 
    array 
     'name' => string 'B' (length=1) 
     'prename' => string 'D' (length=1)) 

功能用於

function __xsort(&$names,$key) { 
    usort($names, function ($a, $b) use($key) { 
     if ($a[$key] == $b[$key]) { 
      return 0; 
     } 
     return ($a[$key] < $b[$key]) ? - 1 : 1; 
    }); 

    return $names; 
}