The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.
YAML_ANY_SCALAR_STYLE
    (integer)
   YAML_PLAIN_SCALAR_STYLE
    (integer)
   YAML_SINGLE_QUOTED_SCALAR_STYLE
    (integer)
   YAML_DOUBLE_QUOTED_SCALAR_STYLE
    (integer)
   YAML_LITERAL_SCALAR_STYLE
    (integer)
   YAML_FOLDED_SCALAR_STYLE
    (integer)
   YAML_NULL_TAG
    (string)
   YAML_BOOL_TAG
    (string)
   YAML_STR_TAG
    (string)
   YAML_INT_TAG
    (string)
   YAML_FLOAT_TAG
    (string)
   YAML_TIMESTAMP_TAG
    (string)
   YAML_SEQ_TAG
    (string)
   YAML_MAP_TAG
    (string)
   YAML_PHP_TAG
    (string)
   YAML_ANY_ENCODING
    (integer)
   YAML_UTF8_ENCODING
    (integer)
   YAML_UTF16LE_ENCODING
    (integer)
   YAML_UTF16BE_ENCODING
    (integer)
   YAML_ANY_BREAK
    (integer)
   YAML_CR_BREAK
    (integer)
   YAML_LN_BREAK
    (integer)
   YAML_CRLN_BREAK
    (integer)