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<refentry xml:id="function.xml-parse-into-struct" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>xml_parse_into_struct</refname>
  <refpurpose>Parse XML data into an array structure</refpurpose>
 </refnamediv>
 
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type class="union"><type>int</type><type>false</type></type><methodname>xml_parse_into_struct</methodname>
   <methodparam><type>XMLParser</type><parameter>parser</parameter></methodparam>
   <methodparam><type>string</type><parameter>data</parameter></methodparam>
   <methodparam><type>array</type><parameter role="reference">values</parameter></methodparam>
   <methodparam choice="opt"><type>array</type><parameter role="reference">index</parameter><initializer>&null;</initializer></methodparam>
  </methodsynopsis>
  <para>
   This function parses an XML string into 2 parallel array structures, one
   (<parameter>index</parameter>) containing pointers to the location of the
   appropriate values in the <parameter>values</parameter> array. These last
   two parameters must be passed by reference.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>parser</parameter></term>
     <listitem>
      <para>
       A reference to the XML parser.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>data</parameter></term>
     <listitem>
      <para>
       A string containing the XML data.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>values</parameter></term>
     <listitem>
      <para>
       An array containing the values of the XML data
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>index</parameter></term>
     <listitem>
      <para>
       An array containing pointers to the location of the appropriate values in the $values.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   <function>xml_parse_into_struct</function> returns 0 for failure and 1 for
   success. This is not the same as &false; and &true;, be careful with
   operators such as ===.
  </para>
 </refsect1>

 <refsect1 role="changelog">
  &reftitle.changelog;
  <informaltable>
   <tgroup cols="2">
    <thead>
     <row>
      <entry>&Version;</entry>
      <entry>&Description;</entry>
     </row>
    </thead>
    <tbody>
     &xml.changelog.parser-param;
    </tbody>
   </tgroup>
  </informaltable>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   Below is an example that illustrates the internal structure of
   the arrays being generated by the function. We use a simple
   <literal>note</literal> tag embedded inside a
   <literal>para</literal> tag, and then we parse this and print out
   the structures generated:
   <example>
    <title><function>xml_parse_into_struct</function> example</title>
    <programlisting role="php">
<![CDATA[
<?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\n";
print_r($index);
echo "\nVals array\n";
print_r($vals);
?>
]]>
    </programlisting>
    <para>
     When we run that code, the output will be:
    </para>
    <screen>
<![CDATA[
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
        )

)
]]>
    </screen>
   </example>
  </para>
  <para>
   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 traversed 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 information:
   <example>
    <title>moldb.xml - small database of molecular information</title>
    <programlisting role="xml">
<![CDATA[
<?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>
]]>
    </programlisting>
   </example>
   And some code to parse the document and generate the appropriate
   objects:
   <example>
    <title>
     parsemoldb.php - parses moldb.xml into an array of
     molecular objects
    </title>
    <programlisting role="php">
<![CDATA[
<?php

class AminoAcid {
    var $name;  // aa name
    var $symbol;    // three letter symbol
    var $code;  // one letter code
    var $type;  // hydrophobic, charged or neutral
    
    function __construct ($aa) 
    {
        foreach ($aa as $k=>$v)
            $this->$k = $aa[$k];
    }
}

function readDatabase($filename) 
{
    // read the XML database of aminoacids
    $data = file_get_contents($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);
}

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

?>
]]>
    </programlisting>
   </example>
   After executing <filename>parsemoldb.php</filename>, the variable
   <varname>$db</varname> contains an array of
   <classname>AminoAcid</classname> objects, and the output of the
   script confirms that:
   <informalexample>
    <screen>
<![CDATA[
** 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
        )

)
]]>
    </screen>
   </informalexample>
  </para>
 </refsect1>

</refentry>
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