xml_parse_into_struct

(PHP 4, PHP 5, PHP 7, PHP 8)

xml_parse_into_struct — Parse XML data into an array structure

Description

xml_parse_into_struct(
    XMLParser$parser,
    string$data,
    array&$values,
    array&$index = null
): int

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

parser: A reference to the XML parser.
data: A string containing the XML data.
values: An array containing the values of the XML data
index: An array containing pointers to the location of the appropriate values in the $values.

Return Values

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

Changelog

Version	Description
8.0.0	`parser` expects an XMLParser instance now; previously, a valid `xml`resource was expected.

Examples

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

Example #1 xml_parse_into_struct() 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\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:

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 __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

 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 ) )