php groupby mysql "group by" 按条件分组

php group by

* groupby.php

<?php

function groupby(array $a, string $prop) {
    return array_reduce($a, function($acc, $obj) use ($prop) {
        $key = $obj[$prop];
        if (!array_key_exists($key, $acc)) {
            $acc[$key] = [];
        }
        array_push($acc[$key], $obj);
        return $acc;
    }, []);
}

function groupby_having(array $a, string $prop, callable $c) {
    return array_reduce($a, function($acc, $obj) use ($prop, $c) {
        if (call_user_func($c, $obj)) {
            $key = $obj[$prop];
            if (!array_key_exists($key, $acc)) {
                $acc[$key] = [];
            }
            array_push($acc[$key], $obj);
        }
        return $acc;
    }, []);
}

// test:

$people = [
    ['id'=>1, 'name'=>'Alice', 'age'=> 21, 'gender'=>'f'],
    ['id'=>2, 'name'=>'Max', 'age'=> 20, 'gender'=>'m'],
    ['id'=>3, 'name'=>'Jack', 'age'=> 20, 'gender'=>'m'],
    ['id'=>4, 'name'=>'Jane', 'age'=> 22, 'gender'=>'f'],
    ['id'=>5, 'name'=>'Steven', 'age'=> 21, 'gender'=>'m']
];

$groupedPeople = groupby($people, 'age');
// var_dump($groupedPeople);
echo json_encode($groupedPeople).PHP_EOL;

$groupedPeople = groupby($people, 'gender');
echo json_encode($groupedPeople).PHP_EOL;

$groupedPeople = groupby_having($people, 'gender', function($row) {
    return $row['age']>20;
});
echo json_encode($groupedPeople).PHP_EOL;

* run:

C:\Users\mingzhanghui\Downloads>php groupby.php

{"21":[{"id":1,"name":"Alice","age":21,"gender":"f"},{"id":5,"name":"Steven","age":21,"gender":"m"}],"20":[{"id":2,"name":"Max","age":20,"gender":"m"},{"id":3,"name":"Jack","age":20,"gender":"m"}],"22":[{"id":4,"name":"Jane","age":22,"gender":"f"}]}

{"f":[{"id":1,"name":"Alice","age":21,"gender":"f"},{"id":4,"name":"Jane","age":22,"gender":"f"}],"m":[{"id":2,"name":"Max","age":20,"gender":"m"},{"id":3,"name":"Jack","age":20,"gender":"m"},{"id":5,"name":"Steven","age":21,"gender":"m"}]}

{"f":[{"id":1,"name":"Alice","age":21,"gender":"f"},{"id":4,"name":"Jane","age":22,"gender":"f"}],"m":[{"id":5,"name":"Steven","age":21,"gender":"m"}]}