=head1 NAME

XML::LibXML::Element - XML::LibXML Class for Element Nodes

=head1 SYNOPSIS

  use XML::LibXML;
  # Only methods specific to Element nodes listed here,
  # see XML::LibXML::Node manpage for other methods

  $node = XML::LibXML::Element->new( $name );
  $node->setAttribute( $aname, $avalue );
  $node->setAttributeNS( $nsURI, $aname, $avalue );
  $avalue = $node->getAttribute( $aname );
  $avalue = $node->setAttributeNS( $nsURI, $aname );
  $attrnode = $node->getAttributeNode( $aname );
  $attrnode = $node->getAttributeNodeNS( $namespaceURI, $aname );
  $node->removeAttribute( $aname );
  $node->removeAttributeNS( $nsURI, $aname );
  $boolean = $node->hasAttribute( $aname );
  $boolean = $node->hasAttributeNS( $nsURI, $aname );
  @nodes = $node->getChildrenByTagName($tagname);
  @nodes = $node->getChildrenByTagNameNS($nsURI,$tagname);
  @nodes = $node->getChildrenByLocalName($localname);
  @nodes = $node->getElementsByTagName($tagname);
  @nodes = $node->getElementsByTagNameNS($nsURI,$localname);
  @nodes = $node->getElementsByLocalName($localname);
  $node->appendWellBalancedChunk( $chunk );
  $node->appendText( $PCDATA );
  $node->appendTextNode( $PCDATA );
  $node->appendTextChild( $childname , $PCDATA );
  $node->setNamespace( $nsURI , $nsPrefix, $activate );
  $node->setNamespaceDeclURI( $nsPrefix, $newURI );
  $node->setNamespaceDeclPrefix( $oldPrefix, $newPrefix );


=head1 DESCRIPTION

=over 4

=item B<new>

  $node = XML::LibXML::Element->new( $name );

This function creates a new node unbound to any DOM.


=item B<setAttribute>

  $node->setAttribute( $aname, $avalue );

This method sets or replaces the node's attribute $aname to the value $avalue


=item B<setAttributeNS>

  $node->setAttributeNS( $nsURI, $aname, $avalue );

Namespace-aware version of setAttribute, where $nsURI is a namespace URI,
$aname is a qualified name, and $avalue is the value. The namespace URI may be
null (empty or undefined) in order to create an attribute which has no
namespace.

The current implementation differs from DOM in the following aspects

If an attribute with the same local name and namespace URI already exists on
the element, but its prefix differs from the prefix of $aname, then this
function is supposed to change the prefix (regardless of namespace declarations
and possible collisions). However, the current implementation does rather the
opposite. If a prefix is declared for the namespace URI in the scope of the
attribute, then the already declared prefix is used, disregarding the prefix
specified in $aname. If no prefix is declared for the namespace, the function
tries to declare the prefix specified in $aname and dies if the prefix is
already taken by some other namespace.

According to DOM Level 2 specification, this method can also be used to create
or modify special attributes used for declaring XML namespaces (which belong to
the namespace "http://www.w3.org/2000/xmlns/" and have prefix or name "xmlns").
This should work since version 1.61, but again the implementation differs from
DOM specification in the following: if a declaration of the same namespace
prefix already exists on the element, then changing its value via this method
automatically changes the namespace of all elements and attributes in its
scope. This is because in libxml2 the namespace URI of an element is not static
but is computed from a pointer to a namespace declaration attribute.


=item B<getAttribute>

  $avalue = $node->getAttribute( $aname );

If $node has an attribute with the name $aname, the value of this attribute
will get returned.


=item B<getAttributeNS>

  $avalue = $node->setAttributeNS( $nsURI, $aname );

Retrieves an attribute value by local name and namespace URI.


=item B<getAttributeNode>

  $attrnode = $node->getAttributeNode( $aname );

Retrieve an attribute node by name. If no attribute with a given name exists,
undef is returned.


=item B<getAttributeNodeNS>

  $attrnode = $node->getAttributeNodeNS( $namespaceURI, $aname );

Retrieves an attribute node by local name and namespace URI. If no attribute
with a given localname and namespace exists, undef is returned.


=item B<removeAttribute>

  $node->removeAttribute( $aname );

The method removes the attribute $aname from the node's attribute list, if the
attribute can be found.


=item B<removeAttributeNS>

  $node->removeAttributeNS( $nsURI, $aname );

Namespace version of removeAttribute


=item B<hasAttribute>

  $boolean = $node->hasAttribute( $aname );

This function tests if the named attribute is set for the node. If the
attribute is specified, TRUE (1) will be returned, otherwise the return value
is FALSE (0).


=item B<hasAttributeNS>

  $boolean = $node->hasAttributeNS( $nsURI, $aname );

namespace version of hasAttribute


=item B<getChildrenByTagName>

  @nodes = $node->getChildrenByTagName($tagname);

The function gives direct access to all child elements of the current node with
a given tagname, where tagname is a qualified name, that is, in case of
namespace usage it may consist of a prefix and local name. This function makes
things a lot easier if one needs to handle big data sets. A special tagname '*'
can be used to match any name.

If this function is called in SCALAR context, it returns the number of elements
found.


=item B<getChildrenByTagNameNS>

  @nodes = $node->getChildrenByTagNameNS($nsURI,$tagname);

Namespace version of getChildrenByTagName. A special nsURI '*' matches any
namespace URI, in which case the function behaves just like
getChildrenByLocalName.

If this function is called in SCALAR context, it returns the number of elements
found.


=item B<getChildrenByLocalName>

  @nodes = $node->getChildrenByLocalName($localname);

The function gives direct access to all child elements of the current node with
a given local name. It makes things a lot easier if one needs to handle big
data sets. A special localname '*' can be used to match any local name.

If this function is called in SCALAR context, it returns the number of elements
found.


=item B<getElementsByTagName>

  @nodes = $node->getElementsByTagName($tagname);

This function is part of the spec. It fetches all descendants of a node with a
given tagname, where tagname is a qualified name, that is, in case of namespace
usage it may consist of a prefix and local name. A special tagname '*' can be
used to match any tag name.

In SCALAR context this function returns a XML::LibXML::NodeList object.


=item B<getElementsByTagNameNS>

  @nodes = $node->getElementsByTagNameNS($nsURI,$localname);

Namespace version of getElementsByTagName as found in the DOM spec. A special
localname '*' can be used to match any local name and nsURI '*' can be used to
match any namespace URI.

In SCALAR context this function returns a XML::LibXML::NodeList object.


=item B<getElementsByLocalName>

  @nodes = $node->getElementsByLocalName($localname);

This function is not found in the DOM specification. It is a mix of
getElementsByTagName and getElementsByTagNameNS. It will fetch all tags
matching the given local-name. This allows one to select tags with the same
local name across namespace borders.

In SCALAR context this function returns a XML::LibXML::NodeList object.


=item B<appendWellBalancedChunk>

  $node->appendWellBalancedChunk( $chunk );

Sometimes it is necessary to append a string coded XML Tree to a node.
appendWellBalancedChunk will do the trick for you. But this is only done if the
String is well-balanced.

Note that appendWellBalancedChunk() is only left for compatibility reasons.
Implicitly it uses

   my $fragment = $parser->parse_xml_chunk( $chunk );
   $node->appendChild( $fragment );

This form is more explicit and makes it easier to control the flow of a script.


=item B<appendText>

  $node->appendText( $PCDATA );

alias for appendTextNode().


=item B<appendTextNode>

  $node->appendTextNode( $PCDATA );

This wrapper function lets you add a string directly to an element node.


=item B<appendTextChild>

  $node->appendTextChild( $childname , $PCDATA );

Somewhat similar with appendTextNode: It lets you set an Element, that contains
only a text node directly by specifying the name and the text content.


=item B<setNamespace>

  $node->setNamespace( $nsURI , $nsPrefix, $activate );

setNamespace() allows one to apply a namespace to an element. The function
takes three parameters: 1. the namespace URI, which is required and the two
optional values prefix, which is the namespace prefix, as it should be used in
child elements or attributes as well as the additional activate parameter. If
prefix is not given, undefined or empty, this function tries to create a
declaration of the default namespace.

The activate parameter is most useful: If this parameter is set to FALSE (0), a
new namespace declaration is simply added to the element while the element's
namespace itself is not altered. Nevertheless, activate is set to TRUE (1) on
default. In this case the namespace is used as the node's effective namespace.
This means the namespace prefix is added to the node name and if there was a
namespace already active for the node, it will be replaced (but its declaration
is not removed from the document). A new namespace declaration is only created
if necessary (that is, if the element is already in the scope of a namespace
declaration associating the prefix with the namespace URI, then this
declaration is reused).

The following example may clarify this:

   my $e1 = $doc->createElement("bar");
   $e1->setNamespace("http://foobar.org", "foo")

results

   <foo:bar xmlns:foo="http://foobar.org"/>

while

   my $e2 = $doc->createElement("bar");
   $e2->setNamespace("http://foobar.org", "foo",0)

results only

   <bar xmlns:foo="http://foobar.org"/>

By using $activate == 0 it is possible to create multiple namespace
declarations on a single element.

The function fails if it is required to create a declaration associating the
prefix with the namespace URI but the element already carries a declaration
with the same prefix but different namespace URI.


=item B<setNamespaceDeclURI>

  $node->setNamespaceDeclURI( $nsPrefix, $newURI );

EXPERIMENTAL IN 1.61 !

This function manipulates directly with an existing namespace declaration on an
element. It takes two parameters: the prefix by which it looks up the namespace
declaration and a new namespace URI which replaces its previous value.

It returns 1 if the namespace declaration was found and changed, 0 otherwise.

All elements and attributes (even those previously unbound from the document)
for which the namespace declaration determines their namespace belong to the
new namespace after the change.

If the new URI is undef or empty, the nodes have no namespace and no prefix
after the change. Namespace declarations once nulled in this way do not further
appear in the serialized output (but do remain in the document for internal
integrity of libxml2 data structures).

This function is NOT part of any DOM API.


=item B<setNamespaceDeclPrefix>

  $node->setNamespaceDeclPrefix( $oldPrefix, $newPrefix );

EXPERIMENTAL IN 1.61 !

This function manipulates directly with an existing namespace declaration on an
element. It takes two parameters: the old prefix by which it looks up the
namespace declaration and a new prefix which is to replace the old one.

The function dies with an error if the element is in the scope of another
declaration whose prefix equals to the new prefix, or if the change should
result in a declaration with a non-empty prefix but empty namespace URI.
Otherwise, it returns 1 if the namespace declaration was found and changed and
0 if not found.

All elements and attributes (even those previously unbound from the document)
for which the namespace declaration determines their namespace change their
prefix to the new value.

If the new prefix is undef or empty, the namespace declaration becomes a
declaration of a default namespace. The corresponding nodes drop their
namespace prefix (but remain in the, now default, namespace). In this case the
function fails, if the containing element is in the scope of another default
namespace declaration.

This function is NOT part of any DOM API.



=back

=head1 AUTHORS

Matt Sergeant, 
Christian Glahn, 
Petr Pajas, 

=head1 VERSION

1.64

=head1 COPYRIGHT

2001-2007, AxKit.com Ltd; 2002-2006 Christian Glahn; 2006-2007 Petr Pajas, All rights reserved.

=cut
