xml_parse_into_struct

xml_parse_into_struct

Parse XML data into an array structure

 **xml_parse_into_struct** XMLParser $parser string $data array $values array $index

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

parserA reference to the XML parser.

dataA string containing the XML data.

valuesAn array containing the values of the XML data

indexAn array containing pointers to the location of the appropriate values in the $values.

returns 0 for failure and 1 for

success. This is not the same as false and true, be careful with operators such as ===. xml_parse_into_struct

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

note``paraVoorbeeld: example

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

And some code to parse the document and generate the appropriate objects:

After executing , the variable contains an array of objects, and the output of the script confirms that:

Voorbeeld: 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>

**Voorbeeld: 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 __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, $tags);
    unset($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);

?>

`$db``AminoAcid````php ** 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
    )

)