如何将数组缩小为多个小数组？

Question

I have this array:

$arr = [{"From"=>"Jack", "To"=>"Peter"},
        {"From"=>"Jack", "To"=>"John"},
        {"From"=>"Jack", "To"=>"Ali"},
        {"From"=>"Ali", "To"=>"Jack"},
        {"From"=>"Ali", "To"=>"Martin"},
        {"From"=>"Jack", "To"=>"Barmar"},
        {"From"=>"Peter", "To"=>"John"}];

Now I need to make multiple array based on From key. I mean, I need to separate them. Something like this:

$arr1 = [{"From"=>"Jack", "To"=>"Peter"},
         {"From"=>"Jack", "To"=>"John"},
         {"From"=>"Jack", "To"=>"Ali"},
         {"From"=>"Jack", "To"=>"Barmar"}];

$arr2 = [{"From"=>"Ali", "To"=>"Jack"},
         {"From"=>"Ali", "To"=>"Martin"}];

$arr3 = [{"From"=>"Peter", "To"=>"John"}];

Has someone any idea how should I do that?

Answer 1

You have to create a new array by some simple implementation of your own logic. Take a look at this simple demonstration:

<?php
$input = [
    ["From"=>"Jack", "To"=>"Peter"],
    ["From"=>"Jack", "To"=>"John"],
    ["From"=>"Jack", "To"=>"Ali"],
    ["From"=>"Ali", "To"=>"Jack"],
    ["From"=>"Ali", "To"=>"Martin"],
    ["From"=>"Jack", "To"=>"Barmar"],
    ["From"=>"Peter", "To"=>"John"]
];
$output = [];

array_walk($input, function($element) use (&$output) {
    $output[$element['From']][] = $element;
});

print_r(array_values($output));

The output of above obviously is:

Array
(
    [0] => Array
        (
            [0] => Array
                (
                    [From] => Jack
                    [To] => Peter
                )

            [1] => Array
                (
                    [From] => Jack
                    [To] => John
                )

            [2] => Array
                (
                    [From] => Jack
                    [To] => Ali
                )

            [3] => Array
                (
                    [From] => Jack
                    [To] => Barmar
                )

        )

    [1] => Array
        (
            [0] => Array
                (
                    [From] => Ali
                    [To] => Jack
                )

            [1] => Array
                (
                    [From] => Ali
                    [To] => Martin
                )

        )

    [2] => Array
        (
            [0] => Array
                (
                    [From] => Peter
                    [To] => John
                )

        )

)