Php无法正确排序数组

Question

I have array:

$test['name1'][256]=[
        'lead_data'=>[
            'datum_event'=>'13.03.2019',
            'address'=>'addr1'
        ]
    ];
    $test['name1'][257]=[
        'lead_data'=>[
            'datum_event'=>'12.02.2019',
            'address'=>'addr2'
        ]
    ];
    $test['name2'][259]=[
        'lead_data'=>[
            'datum_event'=>'15.03.2019',
            'address'=>'addr4'
        ]
    ];
    $test['name2'][260]=[
        'lead_data'=>[
            'datum_event'=>'10.03.2019',
            'address'=>'addr5'
        ]
        ];

    $test['name2'][261]=[
        'lead_data'=>[
            'datum_event'=>'10.02.2019',
            'address'=>'addr10'
        ]
    ];

I need sort groups 'name1' and 'name2' by the smallest 'datum_event' value . So group 'name2' must be first, bacuse there is the smallest datum_event = '10.02.2019' . Also need sort inner arrays by datum_event (from smallest ti heighest). My code is:

function getMinDate($e) {
        return min(array_column(array_column($e, "lead_data"), "datum_event"));
    }

uasort($test, function ($a, $b) {return strcmp(getMinDate($b), getMinDate($a));});

foreach($test as &$e) {
            uasort($e, function ($a, $b) {
                return strcmp($a['lead_data']['datum_event'], $b['lead_data']['datum_event']);});
        }

By i cant get correct output, group 'name2' is second, but must be first. Please , how can i solve this?

Answer 1

Your dates are strings that are not in a sortable format, so you'll need to convert all of them into something sortable before the sort will work. d.m.Y will not sort properly, but if you convert them to Y-m-d format or timestamps it will work. I think it will be more efficient to do this once before you sort rather than repeatedly within the comparison function. So pre-process the name* arrays to determine the minimum date.

foreach ($test as $name => $leads) {
    $test[$name]['min_date'] = min(array_map(function($lead){
        return date_create($lead['lead_data']['datum_event'])->format('U');
    }, $leads));
}

Then sort by that new key.

uasort($test, function($a, $b) {
    return $a['min_date'] <=> $b['min_date'];
});

You can remove the sort key after sorting if you need to.

foreach ($test as $name => $leads) {
    unset($test[$name]['min_date']);
}