Description:
------------
Several tag keys are converted to an integer value (0 or 1) when the key can be interpreted as a boolean (like y, yes, true, off, no). This only happens when the tag is not quoted.

Test script:
---------------
<?php
$yaml = <<<YAML
- 
  x: 147
  y: 85
  z: 176
YAML;
var_dump(yaml_parse($yaml));

Expected result:
----------------
array(2) {
  [0]=>
  array(3) {
    ["x"]=>
    int(147)
    ["y"]=>
    int(85)
    ["z"]=>
    int(176)
  }
}

Actual result:
--------------
array(2) {
  [0]=>
  array(3) {
    ["x"]=>
    int(147)
    [1]=>
    int(85)
    ["z"]=>
    int(176)
  }
}