php data transform

index.php

<?php


$input = array(
  array(
    'category1' => 'foo',
    'category2' => 'bar',
    'value' => 5,
  ),
  array(
    'category1' => 'foo',
    'category2' => 'bar',
    'value' => 7,
  ),
  array(
    'category1' => 'foo',
    'category2' => 'baz',
    'value' => 3,
  ),
);


$output = array(
'foo' => array(
    'bar' => array(
      5,
      7
    )
    'baz'=> array(
      3
    )
  )
);