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.
XML_ERROR_NONE 
    (integer)
   XML_ERROR_NO_MEMORY 
    (integer)
   XML_ERROR_SYNTAX 
    (integer)
   XML_ERROR_NO_ELEMENTS 
    (integer)
   XML_ERROR_INVALID_TOKEN 
    (integer)
   XML_ERROR_UNCLOSED_TOKEN 
    (integer)
   XML_ERROR_PARTIAL_CHAR 
    (integer)
   XML_ERROR_TAG_MISMATCH 
    (integer)
   XML_ERROR_DUPLICATE_ATTRIBUTE 
    (integer)
   XML_ERROR_JUNK_AFTER_DOC_ELEMENT 
    (integer)
   XML_ERROR_PARAM_ENTITY_REF 
    (integer)
   XML_ERROR_UNDEFINED_ENTITY 
    (integer)
   XML_ERROR_RECURSIVE_ENTITY_REF 
    (integer)
   XML_ERROR_ASYNC_ENTITY 
    (integer)
   XML_ERROR_BAD_CHAR_REF 
    (integer)
   XML_ERROR_BINARY_ENTITY_REF 
    (integer)
   XML_ERROR_ATTRIBUTE_EXTERNAL_ENTITY_REF 
    (integer)
   XML_ERROR_MISPLACED_XML_PI 
    (integer)
   XML_ERROR_UNKNOWN_ENCODING 
    (integer)
   XML_ERROR_INCORRECT_ENCODING 
    (integer)
   XML_ERROR_UNCLOSED_CDATA_SECTION 
    (integer)
   XML_ERROR_EXTERNAL_ENTITY_HANDLING 
    (integer)
   XML_OPTION_CASE_FOLDING 
    (integer)
   XML_OPTION_TARGET_ENCODING 
    (integer)
   XML_OPTION_SKIP_WHITE 
    (integer)
   XML_SAX_IMPL 
    (string)