PHP中关联数组的串联

Question

I'm trying to achieve proper merging of two associative arrays:

$year = array(
 array('name' => '2020'),
 array('name' => '2019'),
 array('name' => '2018'),
 array('name' => '2017')
);

$meeting = array(
 array(
    'name' => 'meeting1',
    'year' => '2020'
 ),
 array(
    'name' => 'meeting2',
    'year' => '2020'
 ),
array(
    'name' => 'meeting3',
    'year' => '2019'
 ),
array(
    'name' => 'meeting4',
    'year' => '2018'
 ),
array(
    'name' => 'meeting5',
    'year' => '2018'
 )
);

The result i desire would look like this:

var_dump($array)

$array = array(
 array(
  '2020' => array(
    array('name' => 'meeting1'),
    array('name' => 'meeting2')
    )
   ),
 array(
  '2019' => array(
    array('name' => 'meeting3')
    )
   ),
 array(
  '2018' => array(
    array('name' => 'meeting4'),
    array('name' => 'meeting5')
    )
   ),
 array(
  '2017' => array()
    )
)

However both "+" operator and array_merge() used on $meeting and $year are producing different results than what I require. Is it possible to do using + operator or array_merge or am I required to use foreach loops ?

Answer 1

There is no PHP native function for group array but as said, simple for loop should do it:

foreach($meeting as $e) {
    $array[$e['year']][] = array('name' => $e['name']);
}

And $array will you have you desire result.

Live example: 3v4l

Edit

If you want all the years from $year just init before as:

foreach($year as $e)
    $array[$e['name']] = [];

And then use the first for loop

So full solution will be:

foreach($year as $e)
    $array[$e['name']] = [];
foreach($meeting as $e)
    $array[$e['year']][] = array('name' => $e['name']);

Answer 2

You might also use a combination of array_map and array_filter . For every year in the $year array you can find the matches in the $meeting array.

$array = array_map(function($y) use ($meeting){
    return [$y["name"] => array_filter($meeting, function($m) use ($y) {
        return $m['year'] == $y['name'];
    })];
}, $year);

See a Php demo