php-doc-en/reference/xml/functions/xml-parse-into-struct.xml

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<!-- $Revision: 1.6 $ -->
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  <refentry id="function.xml-parse-into-struct">
   <refnamediv>
    <refname>xml_parse_into_struct</refname>
    <refpurpose>Parse XML data into an array structure</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <methodsynopsis>
     <type>int</type><methodname>xml_parse_into_struct</methodname>
     <methodparam><type>resource</type><parameter>parser</parameter></methodparam>
     <methodparam><type>string</type><parameter>data</parameter></methodparam>
     <methodparam><type>array</type><parameter>&amp;values</parameter></methodparam>
     <methodparam choice="opt"><type>array</type><parameter>&amp;index</parameter></methodparam>
    </methodsynopsis>
    <para>
     This function parses an XML file 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>
    <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 an print out
     the structures generated:
     <informalexample>
      <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>
     </informalexample>
    </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 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 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 and 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 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);
}

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