This is entirely dependent on type detection - as far as I can find there is no way to force a type and for instance when you have a very long integer as a value - in my case 1313035348823 it gets limited to 2147483647 - PHP's max integer.
(PECL yaml >= 0.4.0)
yaml_parse_file — Parse a YAML stream from a file
$pos= 0 [, int
Convert all or part of a YAML document stream read from a file to a PHP variable.
Path to the file.
Document to extract from stream (-1 for all documents, 0 for first document, ...).
ndocs is provided, then it is filled with the
number of documents found in stream.
Returns the value encoded in
input in appropriate
PHP type or
FALSE on failure. If
pos is -1 an
array will be returned with one entry for each document found
in the stream.