<?php

  $array = array(
    'zero', 'one', 'two', 'three'
  );

  echo "zero int: ".$array[0]."\n";
  echo "zero str: ".$array['0']."\n";

  foreach ($array as $key => $value) {
    echo "$key: $value, ".gettype($key)."\n";
  }

  echo "\n";

  $array = array(
    '0' => 'zero', '1' => 'one',
    '2' => 'two', '3' => 'three'
  );

  echo "zero int: ".$array[0]."\n";
  echo "zero str: ".$array['0']."\n";

  foreach ($array as $key => $value) {
    echo "$key: $value, ".gettype($key)."\n";
  }

  echo "\n";

  $array = array(
    '0' => 'zero', '1' => 'one',
    'two' => 'two', '3' => 'three'
  );

  echo "zero int: ".$array[0]."\n";
  echo "zero str: ".$array['0']."\n";

  foreach ($array as $key => $value) {
    echo "$key: $value, ".gettype($key)."\n";
  }

zero int: zero
zero str: zero
0: zero, integer
1: one, integer
2: two, integer
3: three, integer

zero int: zero
zero str: zero
0: zero, integer
1: one, integer
2: two, integer
3: three, integer

zero int: zero
zero str: zero
0: zero, integer
1: one, integer
two: two, string
3: three, integer