XML_PARSE_INTO_STRUCT(3)						 1						  XML_PARSE_INTO_STRUCT(3)

xml_parse_into_struct - Parse XML data into an array structure

SYNOPSIS

       int xml_parse_into_struct (resource  $parser, string  $data, array  &$values, [array  &$index])

DESCRIPTION

	This  function	parses an XML string into 2 parallel array structures, one ($index) containing pointers to the location of the appropriate
       values in the $values array. These last two parameters must be passed by reference.

PARAMETERS

	      o $parser
		- A reference to the XML parser.

	      o $data
		- A string containing the XML data.

	      o $values
		- An array containing the values of the XML data

	      o $index
		- An array containing pointers to the location of the appropriate values in the $values.

RETURN VALUES

       xml_parse_into_struct(3) returns 0 for failure and 1 for success. This is not the same as FALSE and TRUE, be careful with operators such as
       ===.

EXAMPLES

	Below is an example that illustrates the internal structure of the arrays being generated by the function. We use a simple note tag embed-
       ded inside a para tag, and then we parse this and print out the structures generated:

       Example #1

	      xml_parse_into_struct(3) example

	      <?php
	      $simple = "<para><note>simple note</note></para>";
	      $p = xml_parser_create();
	      xml_parse_into_struct($p, $simple, $vals, $index);
	      xml_parser_free($p);
	      echo "Index array
";
	      print_r($index);
	      echo "
Vals array
";
	      print_r($vals);
	      ?>

	       When we run that code, the output will be:

	      Index array
	      Array
	      (
		  [PARA] => Array
		      (
			  [0] => 0
			  [1] => 2
		      )

		  [NOTE] => Array
		      (
			  [0] => 1
		      )

	      )

	      Vals array
	      Array
	      (
		  [0] => Array
		      (
			  [tag] => PARA
			  [type] => open
			  [level] => 1
		      )

		  [1] => Array
		      (
			  [tag] => NOTE
			  [type] => complete
			  [level] => 2
			  [value] => simple note
		      )

		  [2] => Array
		      (
			  [tag] => PARA
			  [type] => close
			  [level] => 1
		      )

	      )

	Event-driven parsing (based on the expat library) can get complicated when you have an XML document that is complex.  This  function  does
       not  produce  a	DOM style object, but it generates structures amenable of being transversed in a tree fashion. Thus, we can create objects
       representing the data in the XML file easily. Let's consider the following XML file representing a small database  of  aminoacids  informa-
       tion:

       Example #2

	      moldb.xml - small database of molecular information

	      <?xml version="1.0"?>
	      <moldb>

		<molecule>
		    <name>Alanine</name>
		    <symbol>ala</symbol>
		    <code>A</code>
		    <type>hydrophobic</type>
		</molecule>

		<molecule>
		    <name>Lysine</name>
		    <symbol>lys</symbol>
		    <code>K</code>
		    <type>charged</type>
		</molecule>

	      </moldb>
	And some code to parse the document and generate the appropriate objects:

       Example #3

	       parsemoldb.php - parses moldb.xml into an array of molecular objects

	      <?php

	      class AminoAcid {
		  var $name;  // aa name
		  var $symbol;	  // three letter symbol
		  var $code;  // one letter code
		  var $type;  // hydrophobic, charged or neutral

		  function AminoAcid ($aa)
		  {
		      foreach ($aa as $k=>$v)
			  $this->$k = $aa[$k];
		  }
	      }

	      function readDatabase($filename)
	      {
		  // read the XML database of aminoacids
		  $data = implode("", file($filename));
		  $parser = xml_parser_create();
		  xml_parser_set_option($parser, XML_OPTION_CASE_FOLDING, 0);
		  xml_parser_set_option($parser, XML_OPTION_SKIP_WHITE, 1);
		  xml_parse_into_struct($parser, $data, $values, $tags);
		  xml_parser_free($parser);

		  // loop through the structures
		  foreach ($tags as $key=>$val) {
		      if ($key == "molecule") {
			  $molranges = $val;
			  // each contiguous pair of array entries are the
			  // lower and upper range for each molecule definition
			  for ($i=0; $i < count($molranges); $i+=2) {
			      $offset = $molranges[$i] + 1;
			      $len = $molranges[$i + 1] - $offset;
			      $tdb[] = parseMol(array_slice($values, $offset, $len));
			  }
		      } else {
			  continue;
		      }
		  }
		  return $tdb;
	      }

	      function parseMol($mvalues)
	      {
		  for ($i=0; $i < count($mvalues); $i++) {
		      $mol[$mvalues[$i]["tag"]] = $mvalues[$i]["value"];
		  }
		  return new AminoAcid($mol);
	      }

	      $db = readDatabase("moldb.xml");
	      echo "** Database of AminoAcid objects:
";
	      print_r($db);

	      ?>
	After executing parsemoldb.php, the variable $db contains an array of AminoAcid objects, and the output of the script confirms that:

       ** Database of AminoAcid objects:
       Array
       (
	   [0] => aminoacid Object
	       (
		   [name] => Alanine
		   [symbol] => ala
		   [code] => A
		   [type] => hydrophobic
	       )

	   [1] => aminoacid Object
	       (
		   [name] => Lysine
		   [symbol] => lys
		   [code] => K
		   [type] => charged
	       )

       )

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