Grouping array items based on string value - php

Question

I am trying to group an array by sport. It could be n number of sports. Finally, then create a new array with it. Is there an efficient way to this without going overkill?
$sports = [
['sport' => 'soccer', 'id' => 97487];
['sport' => 'soccer', 'id' => 244800];
['sport' => 'soccer', 'id' => 258740];
['sport' => 'basketball', 'id' => 147884];
['sport' => 'baseball', 'id' => 222240];
['sport' => 'baseball', 'id' => 222245];
];
Initial array:
array(6) {
[0]=>
array(2) {
["sport"]=>
string(6) "soccer"
["id"]=>
int(97487)
}
[1]=>
array(2) {
["sport"]=>
string(6) "soccer"
["id"]=>
int(244800)
}
[2]=>
array(2) {
["sport"]=>
string(6) "soccer"
["id"]=>
int(258740)
}
[3]=>
array(2) {
["sport"]=>
string(10) "basketball"
["id"]=>
int(147884)
}
[4]=>
array(2) {
["sport"]=>
string(8) "baseball"
["id"]=>
int(222240)
}
[5]=>
array(2) {
["sport"]=>
string(8) "baseball"
["id"]=>
int(222245)
}
}
Desired results:
array(3)
{
[0]=>
array(3) {
[0]=>
array(2) {
["sport"]=>
string(6) "soccer"
["id"]=>
int(97487)
}
[1]=>
array(2) {
["sport"]=>
string(6) "soccer"
["id"]=>
int(244800)
}
[2]=>
array(2) {
["sport"]=>
string(6) "soccer"
["id"]=>
int(258740)
}
}
[1]=>
array(1) {
[0]=>
array(2) {
["sport"]=>
string(10) "basketball"
["id"]=>
int(147884)
}
}
[2]=>
array(2) {
[0]=>
array(2) {
["sport"]=>
string(8) "baseball"
["id"]=>
int(222240)
}
[1]=>
array(2) {
["sport"]=>
string(8) "baseball"
["id"]=>
int(222245)
}
}
}

Answer 1

You can group the array like so:
$sports = [
['sport' => 'soccer', 'id' => 97487],
['sport' => 'soccer', 'id' => 244800],
['sport' => 'soccer', 'id' => 258740],
['sport' => 'basketball', 'id' => 147884],
['sport' => 'baseball', 'id' => 222240],
['sport' => 'baseball', 'id' => 222245]
];
// we will build an array here where the key is the sport
// name and the value is an array of objects pertaining
// to that sport i.e. 'basketball' => [bb1, bb2, ...]
$array = array();
// now consider every sport object in your original array
foreach($sports as $key => $item)
{
if (array_key_exists($item['sport'], $array)) {
// we encountered this same sport in the past so we
// know $array['sportName'] already exists and can
// push right to it
$array[$item['sport']][] = $item;
} else {
// we have never seen this sport before and now must
// insert the sport into $array['sportName'] = []
// and push this sport object to it
$array[$item['sport']] = [$item];
}
}
// since $array's keys are the names of the sports themselves, but
// you want the keys to be numeric, this will build a new array
// from just the values of $array which at this point contains
// grouped arrays of sport objects
$result = array_values($array);
// print the results for good measure :)
print_r($result);
This works by looping over your sports array and building a second array of [sportName => arrayOfThatSport]. Inside the for loop, we are checking to see if a given sport already exists in this array. If it does, great, add the sport to the corresponding array for that sport. Otherwise, create a new array for that sport available at $array['sportName'] = [sportObject]. If you consider several iterations of the loop you will see that we're either always adding to an existing $array['sportName'] array, or creating a new array at this position whenever we encounter a new sport we've never seen before. This gives us a final array similar to: [ "sport
: [...], "sport2": [...] ] but in your case you want a numeric array not an associative array, hence the call to array_values.

Answer 2

This is my suggested solution.
$groupedSports = [];
foreach ($sports as $item) {
if (empty($groupedSports[$item['sport']])) {
$groupedSports[$item['sport']] = [];
}
$groupedSports[$item['sport']][] = $item;
}
Short explanation:
line 1: we initialize an empty array
line 2: we start a loop on the original array
line 3-5: if it's the first occurrence for the current sport, we initialize an empty array for that sport (avoid warnings)
line 6: we assign current item to the appropriate array