PHP比较数组结果和过滤器

Question

I have a php array that looks like this:

Array(
[3086] => Array
    (
        [id] => 3086
        [note] => Make text larger
        [revision] => 1
        [noteParentId] => 1706
    )

[3087] => Array
    (
        [id] => 3087
        [note] => Make text larger
        [revision] => 2
        [noteParentId] => 1706
    )

[3085] => Array
    (
        [id] => 3085
        [note] => Enlarge this image
        [revision] => 1
        [noteParentId] => 1705
    )

[3084] => Array
    (
        [id] => 3086
        [note] => Another test note
        [revision] => 1
        [noteParentId] => 1704
    )

)

How can I filter it in such a way that if the [noteParentId] has the same value (as seen in [3086] and [3087] ), then remove the one with the lower [revision] value from the array?

Answer 1

You should sort the array

function mysort($a, $b){
    if ($a['revision'] >= $b['revision'])
        return 1;
    return -1;
}

and then store the matching values in another array

$arrResult = array();
usort($arrTest, "mysort");
foreach ($arrTest as $key=>$value){
    if (!isset($arrResult[$value['noteParentId']]))
        $arrResult[$value['noteParentId']] = array($key=>$value);
}

Now you will need to sanitize $arrResult...

Answer 2

You can use the array_filter function http://php.net/manual/en/function.array-filter.php

example:

$parentId = 1706;
$filtered = array_filter($data, function($item) use ($parentId) { 
   return $item['noteParentId'] === $parentId; 
});

or if you modify the sql query, you can use group by and filter by count(parent_id) > 1

example:

SELECT noteParentId, count(*) FROM someTable GROUP BY noteParentId WHERE count(*) > 1;

Answer 3

This answer will require a little more code than the previous answers, but I think it's a more efficient solution for the following reasons:

• It will always be a O(n) solution for you
• It keeps the same data structure you expected
• It won't require you to merge multiple filtered result sets. and merges of data.

////

function filterOldRevisions($tasks) {

    $revisionHash = array();

    foreach ($tasks as $taskId => $task) {
        if (isset($revisionHash[$task['noteParentId']])) {
            $currentMaxRevision = $revisionHash[$task['noteParentId']];

            if ($task['revision'] > $revisionHash[$task['noteParentId']]) {
                //store the max revision for the parent in the hash
                $previousMaxId = $revisionHash[$task['noteParentId']]['id'];
                $revisionHash[$task['parentId']]  = $task;

                //remove the previous max revision
                unset($tasks[$previousMaxId]);
            } else {
                //remove lower revision
                unset($tasks[$taskId]);
            }
        } else {
            //always store the first task
            $revisionHash[$task['noteParentId']]  = $task;
        }
    }

    return $tasks;
}