xml_parse_into_struct
(PHP 3>= 3.0.8, PHP 4 , PHP 5)
xml_parse_into_struct -- Parse XML data into an array structure
Description
int
xml_parse_into_struct ( resource parser, string data, array &values [, array &index])
This function parses an XML file 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.
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);
?>
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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 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> |
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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);
}
$db = readDatabase("moldb.xml");
echo "** Database of AminoAcid objects:\n";
print_r($db);
?>
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After executing
parsemoldb.php, the variable
$db contains an array of
AminoAcid objects, and the output of the
script confirms that: