Structural Extraction of PHP Arrays

xtract.md

Structural Extraction of PHP Arrays

Extract structures from PHP arrays, kind of like an advanced pluck.

Signature

The provided xtract function takes a $source (usually an array) and a $target, which is the structure to transform the $source into:

mixed xtract( mixed $source, mixed $target )

Simple Examples

xtract([ 1, 2, 3 ], [ 0, 1 ]) === [ 1, 2 ];

// The asterisk is a special token, translating to "anything"
xtract([ 1, 2, 3 ], '*') === [ 1, 2, 3 ];

Advanced Examples

$source = [
    'a' => [
        'd' => 3,
        'e' => 4
    ],
    'b' => [
        'd' => 5,
        'e' => 6
    ],
    'c' => [
        'd' => 7,
        'e' => 8
    ]
];

xtract($source, [ 'a' ])
===
[
    'a' => [
        'd' => 3,
        'e' => 4
    ]
];

xtract($source, [ '*' => [ 'd' ] ])
===
[
    'a' => [ 'd' => 3 ],
    'b' => [ 'd' => 5 ],
    'c' => [ 'd' => 7 ]
];

xtract.php

<?php

function xtract($source, $target)
{
    if ($target === '*') {
        return $source;
    }
    
    $result = [];

    if (sizeof($target) === 1 && isset($target['*'])) {
        foreach ($source as $k => $v) {
            $result[$k] = xtract($v, $target['*']);
        }
    } else {
        $i = 0;
        foreach ($target as $k => $v) {
            $nested = $i !== $k;
            $key = $nested ? $k : $v;

            if (isset($source[$key])) {
                $result[$key] = $nested
                    ? xtract($source[$key], $v)
                    : $source[$key];
            }
            
            if (!is_string($k)) {
                $i++;
            }
        }
    }

    return $result;
}