Set up unparsed entity declaration handler

# xml_set_unparsed_entity_decl_handler

(PHP 4, PHP 5, PHP 7, PHP 8)

xml_set_unparsed_entity_decl_handler — Set up unparsed entity declaration handler

### Description

xml_set_unparsed_entity_decl_handler(XMLParser `$parser`, callable|string|null `$handler`): true

Sets the unparsed entity declaration handler function for the XML parser `parser`.

The `handler` will be called if the XML parser encounters an external entity declaration with an NDATA declaration, like the following:

    <!ENTITY <parameter>name</parameter> {<parameter>publicId</parameter> | <parameter>systemId</parameter>}
            NDATA <parameter>notationName</parameter>

See » section 4.2.2 of the XML 1.0 spec for the definition of notation declared external entities.

### Parameters

`parser`

  The XML parser.

`handler`

  If `null` is passed, the handler is reset to its default state.

  Warning

  An empty string will also reset the handler, however this is deprecated as of PHP 8.4.0.

  If `handler` is a callable, the callable is set as the handler.

  If `handler` is a string, it can be the name of a method of an object set with xml_set_object().

  Warning

  This is deprecated as of PHP 8.4.0.

  Warning

  As of PHP 8.4.0, the callable is checked to be valid while setting the handler, not when it is called. This means that xml_set_object() must be called prior to setting a method string as the callback. However, as this behaviour is also deprecated as of PHP 8.4.0, using a proper callable for the method is recommended instead.

  The signature of the handler must be:

  handler(
  XMLParser `$parser`,
  string `$entity_name`,
  string|false `$base`,
  string `$system_id`,
  string|false `$public_id`,
  string|false `$notation_name`
  ): void
  `parser`
    The XML parser calling the handler.
  `entity_name`
    The name of the entity that is about to be defined.
  `base`
    This is the base for resolving the system identifier (`systemId`) of the external entity.
  `system_id`
    System identifier for the external entity.
  `public_id`
    Public identifier for the external entity.
  `notation_name`
    Name of the notation of this entity (see xml_set_notation_decl_handler()).

### Return Values

Always returns `true`.

### Changelog

Version | Description
--- | ---
8.4.0 | Passing a non-callable string to `handler` is now deprecated, use a proper callable for methods, or `null` to reset the handler.
8.4.0 | The validity of `handler` as a callable is now checked when setting the handler instead of checking when calling it.
8.0.0 | `parser` expects an XMLParser instance now; previously, a valid `xml` resource was expected.

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