更简洁的方法来在多维数组中提取动态嵌套元素以进行排序
Is there a cleaner way to extract a nested value from a 3 level deep multidimensional array, where i want to pull the result stacked inside the 3rd level, hwoever, i want to keep this dynamic so i can also grab elem from 2nd or 4th level by using an array as a parameter to determine this.
what im trying to do in the end is SORT using this element, but i cant find a way to conveniently indicate the element chain except for this way which i had to create myself:
public function keyBySubElement($nestedArray, array $subElemStack){
//essentially the loop below is doing this, but it is dynamic now so a user can specify different nested levels in the $subElemStack param.
//$nestedValue = $nestedArray[$subElemStack[0]][$subElemStack[1]];
foreach($subElemStack as $nestedElement){
if(isset($nestedValue) && is_array($nestedValue))
{
$nestedValue = $nestedValue[$nestedElement];
}
else
{
$nestedValue = $nestedArray[$nestedElement];
}
}
return $nestedValue;
}
e.g. to use this method:
assume the following data
$searchResults = array(
0 => array(
'title' => 'one',
array(
'ratings' => array(
'count' => '1'
)
)
),
1 => array(
'title' => 'two',
array(
'ratings' => array(
'count' => '5'
)
)
),
2 => array(
'title' => 'three',
array(
'ratings' => array(
'count' => '2'
)
)
),
);
foreach($searchResults as $k => $v){
$count = $this->keyBySubElement($v, array('ratings','count'));
$sortData[$k] = $count;
}
this gives me something like this
array(4) {
[0]=>
int(1)
[1]=>
int(5)
[2]=>
int(2)
}
now that i have access to my sub-sub elements value, tied in with its top level parent key, i can use it to sort the top level array by key using my new array $sortData as the reference key which can be reordered by the sub elements value that i want to sort with. i was next going just re-sort the original array by the new key values or something.
i saw a couple potential good examples, but i wasn't able to make them work. those examples are as follows:
[PHP sort: user function][1]
e.g. 1) http://php.net/manual/en/function.sort.php#99419
e.g. 2) Sort php multidimensional array by sub-value
e.g. 3)
/**
* Sort a 2 dimensional array based on 1 or more indexes.
*
* msort() can be used to sort a rowset like array on one or more
* 'headers' (keys in the 2th array).
*
* @param array $array The array to sort.
* @param string|array $key The index(es) to sort the array on.
* @param int $sort_flags The optional parameter to modify the sorting
* behavior. This parameter does not work when
* supplying an array in the $key parameter.
*
* @return array The sorted array.
*/
public function msort($array, $key, $sort_flags = SORT_REGULAR) {
if (is_array($array) && count($array) > 0) {
if (!empty($key)) {
$mapping = array();
foreach ($array as $k => $v) {
$sort_key = '';
if (!is_array($key)) {
$sort_key = $v[$key];
} else {
// @TODO This should be fixed, now it will be sorted as string
foreach ($key as $key_key) {
$sort_key .= $v[$key_key];
}
$sort_flags = SORT_STRING;
}
$mapping[$k] = $sort_key;
}
asort($mapping, $sort_flags);
$sorted = array();
foreach ($mapping as $k => $v) {
$sorted[] = $array[$k];
}
return $sorted;
}
}
return $array;
}
e.g. 4)
/**
* @param $array
* @param $cols
* @return array
*/
public function array_msort($array, $cols)
{
$colarr = array();
foreach ($cols as $col
=> $order) {
$colarr[$col] = array();
foreach ($array as $k => $row) {
$colarr[$col]['_'.$k] = strtolower($row[$col]);
}
}
$eval = 'array_multisort(';
foreach ($cols as $col => $order) {
$eval .= '$colarr[\''.$col.'\'],'.$order.',';
}
$eval = substr($eval,0,-1).');';
eval($eval);
$ret = array();
foreach ($colarr as $col => $arr) {
foreach ($arr as $k => $v) {
$k = substr($k,1);
if (!isset($ret[$k])) $ret[$k] = $array[$k];
$ret[$k][$col] = $array[$k][$col];
}
}
return $ret;
}
Since the data structure that they return is rather ugly and not condusive to sorting, my first move would be to reformat it into something that can be easily sorted. For example:
# create a new key, 'ratings', and put the contents of [0][ratings][count] in it
foreach ($searchResults as &$s) {
print_r($s);
# you could use your keybysubelement function to retrieve the value here
# rather than hardcoding it
$s['ratings'] = $s[0]['ratings']['count'];
unset($s[0]);
}
print_r($searchResults);
resulting data structure:
Array
(
[0] => Array
(
[title] => one
[ratings] => 1
)
[1] => Array
(
[title] => two
[ratings] => 5
)
[2] => Array
(
[title] => three
[ratings] => 2
)
)
It's then easy to create a sort function that will operate on this array to sort it according to the value in 'ratings':
# create a closure that will sort by a given key and in a given direction
# by default the order is ascending
function by_key($key, $dir = 'asc') {
return function ($a, $b) use ($key, $dir) {
if ($a[$key] > $b[$key]) {
if ($dir === 'asc')
return 1;
return -1;
}
elseif ($a[$key] < $b[$key]) {
if ($dir === 'asc')
return -1;
return 1;
}
return 0;
};
}
# sort by ratings, descending, using uasort and the custom search function:
uasort( $searchResults, by_key('ratings','desc') );
# print the results
foreach ($searchResults as $i) {
echo $i['title'] . ', ' . $i['ratings'] . PHP_EOL;
}
array order after sort:
two, 5
three, 2
one, 1
Sort by title:
uasort( $searchResults, by_key('title') );
Output:
one, 1
three, 2
two, 5