PHP xml_set_unparsed_entity_decl_handler() Function

<?php
$parser=xml_parser_create();

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

function unparsed_ent_handler($parser,$entname,$base,$sysID,$pubID,$notname) {
  print "$entname<br>";
  print "$sysID<br>";
  print "$pubID<br>";
  print "$notname<br>";
}

xml_set_character_data_handler($parser,"char");
// Set up unparsed entity declaration handler
xml_set_unparsed_entity_decl_handler($parser,"unparsed_ent_handler");

$fp=fopen("test.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);
?>