如何按多列对多维数组排序? [英] How to sort a multidimensional array by multiple columns?
问题描述
我正在尝试与MySQL查询相同
I'm trying to do the same as MySQL query
SELECT * FROM table ORDER BY field1, field2, ...
但使用php和多维数组:
but with php and a multidimensional array:
$Test = array(
array("a"=>"004", "n"=>"03"),
array("a"=>"003", "n"=>"02"),
array("a"=>"001", "n"=>"02"),
array("a"=>"005", "n"=>"01"),
array("a"=>"001", "n"=>"01"),
array("a"=>"004", "n"=>"02"),
array("a"=>"003", "n"=>"01"),
array("a"=>"004", "n"=>"01")
);
function msort(&$array, $keys){
array_reverse($keys);
foreach($keys as $key){
uasort($array, sortByKey);
}
//
function sortByKey($A, $B){
global $key;
$a = $A[$key];
$b = $B[$key];
if($a==$b) return 0;
return ($a < $b)? -1 : 1 ;
}
}
//
msort($Test, array("a","n"));
//
foreach($Test as $t){
echo('<p>'.$t["a"].'-'.$t["n"].'</p>');
}
我的理论是:如果对重要性较低"的列进行多次排序,然后对重要性较高"的列进行多次排序,则将获得类似于上述MySQL查询的顺序.
My theory is: if I sort multiple times on columns with "lesser importance" then columns of "greater importance", I'll achieve an order like the above MySQL query.
不幸的是,php返回:
Unfortunately, php is returning:
警告:uasort()期望参数2为有效的回调,函数'sortByKey'未找到或/Library/WebServer/Documents/www/teste.array_sort.php的第23行(uasort行)上的函数名称无效
Warning: uasort() expects parameter 2 to be a valid callback, function 'sortByKey' not found or invalid function name in /Library/WebServer/Documents/www/teste.array_sort.php on line 23" (uasort line)
这是一个简单的订购功能.我想念什么?
It's a simple order function. What am I missing?
推荐答案
基本上,我们将使用与此处解释的方法相同的方法,我们将使用可变数量的键来完成此操作:
Fundamentally we're going to use the same approach as explained here, we're just going to do it with a variable number of keys:
/**
* Returns a comparison function to sort by $cmp
* over multiple keys. First argument is the comparison
* function, all following arguments are the keys to
* sort by.
*/
function createMultiKeyCmpFunc($cmp, $key /* , keys... */) {
$keys = func_get_args();
array_shift($keys);
return function (array $a, array $b) use ($cmp, $keys) {
return array_reduce($keys, function ($result, $key) use ($cmp, $a, $b) {
return $result ?: call_user_func($cmp, $a[$key], $b[$key]);
});
};
}
usort($array, createMultiKeyCmpFunc('strcmp', 'foo', 'bar', 'baz'));
// or
usort($array, createMultiKeyCmpFunc(function ($a, $b) { return $a - $b; }, 'foo', 'bar', 'baz'));
这等效于SQL ORDER BY foo, bar, baz
.
如果每个键当然都需要不同种类的比较逻辑,并且您不能对所有键都使用通用的strcmp
或-
,那么您将返回与
If of course each key requires a different kind of comparison logic and you cannot use a general strcmp
or -
for all keys, you're back to the same code as explained here.
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