# Predefined Constants

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` (int)
`XML_ERROR_NO_MEMORY` (int)
`XML_ERROR_SYNTAX` (int)
`XML_ERROR_NO_ELEMENTS` (int)
`XML_ERROR_INVALID_TOKEN` (int)
`XML_ERROR_UNCLOSED_TOKEN` (int)
`XML_ERROR_PARTIAL_CHAR` (int)
`XML_ERROR_TAG_MISMATCH` (int)
`XML_ERROR_DUPLICATE_ATTRIBUTE` (int)
`XML_ERROR_JUNK_AFTER_DOC_ELEMENT` (int)
`XML_ERROR_PARAM_ENTITY_REF` (int)
`XML_ERROR_UNDEFINED_ENTITY` (int)
`XML_ERROR_RECURSIVE_ENTITY_REF` (int)
`XML_ERROR_ASYNC_ENTITY` (int)
`XML_ERROR_BAD_CHAR_REF` (int)
`XML_ERROR_BINARY_ENTITY_REF` (int)
`XML_ERROR_ATTRIBUTE_EXTERNAL_ENTITY_REF` (int)
`XML_ERROR_MISPLACED_XML_PI` (int)
`XML_ERROR_UNKNOWN_ENCODING` (int)
`XML_ERROR_INCORRECT_ENCODING` (int)
`XML_ERROR_UNCLOSED_CDATA_SECTION` (int)
`XML_ERROR_EXTERNAL_ENTITY_HANDLING` (int)
`XML_OPTION_CASE_FOLDING` (int)
`XML_OPTION_PARSE_HUGE` (int)
  Available as of PHP 8.4.0. When libxml2 < 2.7.0 is used (e.g. on PHP 7.x), this option is enabled by default and cannot be disabled.
`XML_OPTION_TARGET_ENCODING` (int)
`XML_OPTION_SKIP_TAGSTART` (int)
`XML_OPTION_SKIP_WHITE` (int)
`XML_SAX_IMPL` (string)
  Holds the SAX implementation method. Can be `libxml` or `expat`.

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