Group by group, calculate the sum of occurrences of each group, and print the data as a formatted string

Question

I want to group and sum the data of some rows based on the values ​​of two columns.

My input is:

$array = [
    ['FA',12.9],
    ['FA',12.9],
    ['FB',12.2],
    ['FC',12.3],
    ['FA',12.9],
    ['FB',12.9],
    ['FA',12.4],
];

I want to print the grouped row values ​​as a string, followed by a x and the total number of occurrences, in the following format:

FA 12.9x3
FB 12.2x3

I've written code to count the occurrences of a value in each group, but I don't know how to print it out in this format:

$new = [];
foreach ($array as $key=> $value) {
    if (!array_key_exists($value[0],$new)) {
        $new[$value[0]]=[strval($value[1])=>1];
    }
    else {
        if (!array_key_exists(strval($value[1]),$new[$value[0]])) {
           $new[$value[0]][strval($value[1])]=1;
           // $no =1;
        }
        else {
            $count= $new[$value[0]];
            $count=$count[strval($value[1])];
            $count =1;
            $new[$value[0]][strval($value[1])]=$count;
        }
    }
}

Can this code be optimized and printed in the correct format?

Desired output:

FA 12.9x3
FB 12.2x1
FC 12.3x1
FB 12.9x1
FA 12.4x1

Answer 1

Using array_reduceIn a special and useful way, we can group items by name. Then group by value and count. The idea is to pass an array with accumulated values ​​as keys.

$g = array($a, $b, $c, $d, $e, $f, $h);

$result = array_reduce($g, function ($carry, $item) {
    $key = $item[0];
    $value = $item[1];
    if (!isset($carry[$key])) {
        $carry[$key] = [];
    }
    if (!isset($carry[$key][(string) $value])) {
        $carry[$key][(string) $value] = 0;
    }
    $carry[$key][(string) $value]++;
    return $carry;
}, []);

print_r($result);

Output:

Array
(
    [FA] => Array
        (
            [12.9] => 3
            [12.4] => 1
        )

    [FB] => Array
        (
            [12.2] => 1
            [12.9] => 1
        )

    [FC] => Array
        (
            [12.3] => 1
        )

)