gistfile1.txt

ARRAY IN:

array(
  array('name' => 'john', 'occupation' => 'electrician'),
  array('name' => 'jack', 'occupation' => 'plumber'),
  array('name' => 'jake', 'occupation' => 'office rat'),
  array('name' => 'pete', 'occupation' => 'electrician')
);

ARRAY OUT:

array(
  'electrician' => array('john', 'pete'),
  'plumber' => array('jack'),
  'office rat' => array('jake')
);