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
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, ...).
If 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. NULL is returned if the input cannot be decoded. If pos is -1 an array will be returned with one entry for each document found in the stream.