# perldoc > XML::LibXML::PI

## NAME
    [XML::LibXML::PI](https://www.chedong.com/phpMan.php/perldoc/XML%3A%3ALibXML%3A%3API/markdown) - [XML::LibXML](https://www.chedong.com/phpMan.php/perldoc/XML%3A%3ALibXML/markdown) Processing Instructions

## SYNOPSIS
      use [XML::LibXML](https://www.chedong.com/phpMan.php/perldoc/XML%3A%3ALibXML/markdown);
      # Only methods specific to Processing Instruction nodes are listed here,
      # see the [XML::LibXML::Node](https://www.chedong.com/phpMan.php/perldoc/XML%3A%3ALibXML%3A%3ANode/markdown) manpage for other methods

      $pinode->setData( $data_string );
      $pinode->setData( name=>string_value [...] );

## DESCRIPTION
    Processing instructions are implemented with [XML::LibXML](https://www.chedong.com/phpMan.php/perldoc/XML%3A%3ALibXML/markdown) with read and write access. The PI data
    is the PI without the PI target (as specified in XML 1.0 [17]) as a string. This string can be
    accessed with getData as implemented in [XML::LibXML::Node](https://www.chedong.com/phpMan.php/perldoc/XML%3A%3ALibXML%3A%3ANode/markdown).

    The write access is aware about the fact, that many processing instructions have attribute like
    data. Therefore setData() provides besides the DOM spec conform Interface to pass a set of named
    parameter. So the code segment

      my $pi = $dom->createProcessingInstruction("abc");
      $pi->setData(foo=>'bar', foobar=>'foobar');
      $dom->appendChild( $pi );

    will result the following PI in the DOM:

      <?abc foo="bar" foobar="foobar"?>

    Which is how it is specified in the DOM specification. This three step interface creates
    temporary a node in perl space. This can be avoided while using the
### insertProcessingInstruction

      $dom->insertProcessingInstruction("abc",'foo="bar" foobar="foobar"');

    will have the same result as above.

    [XML::LibXML::PI](https://www.chedong.com/phpMan.php/perldoc/XML%3A%3ALibXML%3A%3API/markdown)'s implementation of setData() documented below differs a bit from the standard
    version as available in [XML::LibXML::Node](https://www.chedong.com/phpMan.php/perldoc/XML%3A%3ALibXML%3A%3ANode/markdown):

    setData
          $pinode->setData( $data_string );
          $pinode->setData( name=>string_value [...] );

        This method allows one to change the content data of a PI. Additionally to the interface
        specified for DOM Level2, the method provides a named parameter interface to set the data.
        This parameter list is converted into a string before it is appended to the PI.

## AUTHORS
    Matt Sergeant, Christian Glahn, Petr Pajas

## VERSION
    2.0134

## COPYRIGHT
    2001-2007, AxKit.com Ltd.

    2002-2006, Christian Glahn.

    2006-2009, Petr Pajas.

## LICENSE
    This program is free software; you can redistribute it and/or modify it under the same terms as
    Perl itself.