<?php

// Foreach creates a copy
$array = array(
  "foo" => array('bar', 'baz'),
  "bar" => array('foo'),
  "baz" => array('bar'),
  "batz" => array('end')
);

// while(list($i, $value) = each($array)) { // Try this next
foreach($array as $i => $value) {
  print $i . "\n";
  foreach($value as $index) {
    unset($array[$index]);
  }
}

print_r($array); // array('baz' => ['end'])

foo
bar
baz
batz
Array
(
    [batz] => Array
        (
            [0] => end
        )

)