Description:
------------
Since 5.6.19RC1 and 7.0.4RC1 the test suite fails:

TEST 11/62 [tests/yaml_002.phpt]
========DIFF========
010+ bool(false)
010- bool(true)
========DONE========
FAIL yaml - emit -> parse roundtrip with datetime [tests/yaml_002.phpt] 

This is related to fix for https://bugs.php.net/71525

Quoting Derick:

I had a look at this again, and the YAML parser simply doesn't encode 
the fractions properly.

Input:
  "canonical" => new DateTime("2001-12-15T02:59:43.1Z"),

YAML created:
  canonical: 2001-12-15T02:59:43+0000

see it misses the ".1" from the original date string

Of course, when you then convert it back to DateTime, it still misses 
the .1:

  'canonical' => string(24) "2001-12-15T02:59:43+0000"

Before this bug fix, the fraction wasn't taking into account when 
comparing. F.e., this would compare as true:

$a = new DateTime("2001-12-15T02:59:43.5Z");
$b = new DateTime("2001-12-15T02:59:43.7Z");

var_dump( $a == $b );

After the bug fix, it (correctly) no longer does that.
So the YAML extension's tests are wrong, or, they need to implement 
support for fractions.

The YAML extension also loses the 'Europe/London' and 'Z' timezone 
information, as in the created YAML just does +0000 and -0500.