Interview question for PHP developers

interview.php

<?php
/*
  Objectives:
    - Create PHP script that will translate input data to expected output from example below.
    - Calculate time complexity of your script
    bonus: Implement solution that will not use pass-by-reference and will not use objects
*/

$input = [
    'A' => 1,
    'B_C' => 2,
    'B_D' => 3,
    'E_F_G' => 4,
    'E_H' => 5
];

$expectedOutput = [
    'A' => 1,
    'B' => [
        'C' => 2,
        'D' => 3
    ],
    'E' => [
        'F' => [
            'G' => 4
        ],
        'H' => 5
    ]
];

foreach($input as $k => $v)
    eval("\$output['".str_replace('_',"']['",$k)."']=$v;");

OK, didn't want to post it here initially, but for the record ;)

https://gist.github.com/foglcz/07ce7e1a1c29bcf28bf6