Converting XML Into a PHP Data Structure - Make PHP Do The Hard Work

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PHP has a built-in process for parsing your XML document. You pass a string to the xml_parse function with XML text in it and when the XML document is parsed, handlers for the configured events are called as many times as necessary.

Some events for which you can write handlers are 'StartElement', 'EndElement', and 'CharacterData'.

Here is some sample code for defining a class and the three event handlers to parse XML:

class XMLToArray
{
var $parser;

//-----------------------------------------
/* Parse a text string containing valid XML into a multidim array. */
function parse($xmlstring="")
{

// set up a new XML parser to do all the work for us
$this->parser = xml_parser_create();
xml_set_object($this->parser, $this);
xml_parser_set_option($this->parser, XML_OPTION_CASE_FOLDING, false);
xml_set_element_handler($this->parser, "startElement", "endElement");
xml_set_character_data_handler($this->parser, "characterData");

// parse the data and free the parser...
xml_parse($this->parser, $xmlstring);
xml_parser_free($this->parser);

// ...
}

//-----------------------------------------
function startElement($parser, $name, $attrs)
{

// Start a new Element. This means we push the new element onto
// the stackand reset it's properties.
printf("START: [%s]\n", $name);

// ...
}

//-----------------------------------------
function endElement($parser, $name)
{

// End an element. This is done by popping the last element from
// the stack and adding it to the previous element on the stack.
printf("END: [%s]\n", $name);

// ...
}

//-----------------------------------------
function characterData($parser, $data) {
// Collect the data onto the end of the current chars.
printf("DATA: [%s]\n", str_replace("\n", "", $data));

// ...
}

//-----------------------------------------
}


Once we've built this class to wrap the PHP parser, we can create an instance of the class and have it parse the XML sample code we described above.

Some sample code to do this would look as follows:

$xml2a = new XMLToArray();
$xml2a->parse($xml_text);

Next: Watching the XML Parsing Events: Callback Functions >>
 

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