PHP xml_set_element_handler() Function

<?php
$parser=xml_parser_create();

function start($parser,$element_name,$element_attrs) {
  switch($element_name) {
    case "NOTE":
    echo "NOTE<br>";
    break;
    case "TO":
    echo "To: ";
    break;
    case "FROM":
    echo "From: ";
    break;
    case "HEADING":
    echo "Heading: ";
    break;
    case "BODY":
    echo "Message: ";
  }
}

function stop($parser,$element_name) {
echo "<br>";
}

function char($parser,$data) {
echo $data;
}

//  Specify functions to be called at the start and end of an element in the XML document
xml_set_element_handler($parser,"start","stop");
xml_set_character_data_handler($parser,"char");
$fp=fopen("note.xml","r");

while ($data=fread($fp,4096)) {
  xml_parse($parser,$data,feof($fp)) or
  die (sprintf("XML Error: %s at line %d",
  xml_error_string(xml_get_error_code($parser)),
  xml_get_current_line_number($parser)));
}

xml_parser_free($parser);
fclose($fp);
?>